desktop gas user`s manual
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1. NBS data not available COMPARISON OF RESULTS WITH NBS 1 DATA TABLE 14 ENTROPY OF CARBON DIOXIDE Temperature Pressure Range deg K deg K Avg Max Avg Max Avg Max Error Error Error Error Error Error A 300 o 002 0 003 0 006 0 014 NA 350 0 001 0 003 0 003 0 005 0 033 0 086 10 700 0 003 0 001 0 001 0 003 0 003 0 006 710 soo 0 003 0 001 0 001 0 003 0 001 0 002 DeskTop Gas for Windows Version 4 0 User s Manual Chapter 4 Accuracy COMPARISON OF RESULTS WITH ASME 6 DATA TABLE 15 ENTROPY OF WATER VAPOR Range degK Avg Max Avg Max Avg Max Error Error Error Error Error Error NA NA From eg K 180 290 80 460 40 10 710 50 1500 m m 0 05896 0 06196 COMPARISON OF RESULTS WITH NBS 1 DATA TABLE 16 SPECIFIC HEAT OF NITROGEN Temperature Pressure Range From eg K 180 260 10 60 410 10 10 710 810 1500 deg K Avg Max Avg Max Avg Max Error Error Error Error Error Error 250 o 062 0 182 0 758 2 899 2 923 9 543 DeskTop Gas for Windows Version 4 0 User s Manual Page 37 Chapter 4 Accuracy Page 38 COMPARISON OF RESULTS WITH NBS 1 DATA TABLE 17 SPECIFIC HEAT OF OXYGEN Range degK deg K Avg Max Avg Max Avg Max re ter ere rer te COMPARISON OF RESULTS WITH NBS 1 DATA TABLE 18 SPECIFIC HEAT OF ARGON Temperature Pressure Range deg K deg K Avg Max Avg Max Avg Max Error Error Error Erro2. 3 3 1 Viscosity We treat the gas as a binary mixture between the non polar gases N O Ar and CO and water vapor For the non polar gases the viscosity of the mixture can be calculated as follows Hy 23 33 34 3 Hy 24 34 44 X4 x x x x 0 H 1 2 2 2 where AY Hy Ay Hy Ay Hy Hg Hy AL H4 H4 Hy Ay Hy Hy Hy H X S2x MM 5 M and m tat Mu M Mi 34 M 2xx MM 5 Hos 4c EM 1 ij 2 ny M M 3A y where n coefficient of viscosity of pure gas component i DeskTop Gas for Windows Version 4 0 User s Manual Chapter 3 Theoretical Basis of Gas Functions Page 23 J2M M TUM M sona Ny 266 93 107 T kT e reduced temperature c T parameters in the potential function characteristic of 1 2 interaction x mole fraction of component i M molecular weight of component i o2 LIIS A Q Q OTP integrals for calculating the transport coefficients for the Leonard Jones 6 12 potential Once we have the viscosity of the non polar gas mixture we can use the equations for a polar non polar mixture The equation for viscosity of a binary mixture is as follows X Y 1 5 LPL where 7 viscosity of the mixture 2 2 ME X n 2x X NS T hc Abu d M M Y JC A 2xx IM M Y mi AM 1 75 T mM m MM Inn m M M M M Z IA x 2x x 7 J Taw e 1 TX M i 7 M R 4MM 1 1j M 8 H
3. COMPARISON OF RESULTS WITH NBS 1 DATA TABLE 1 COMPRESSIBILITY OF NITROGEN Pressure Range Error Error Error Error Error Error Error Error Bro Fa fo 000 p oon o ooo J 001 001 o noe Jo 007 Dos COMPARISON OF RESULTS WITH NBS 1 DATA TABLE 2 COMPRESSIBILITY OF OXYGEN Tempe Pressure Ran rature ge Error Error Error Error Error Error Error Error pen 250 am CM 400 _ 0 000 0 000 0 000 10 000 0 001 0 002 0 004 10 006 500 eoo zoo TM 1450 degK 250 300 350 400 500 700 800 1450 2 DeskTop Gas for Windows Version 4 0 User s Manual Chapter 4 Accuracy COMPARISON OF RESULTS WITH NBS 1 DATA TABLE 3 COMPRESSIBILITY OF ARGON Temperature Pressure Range egK 180 260 310 360 410 10 610 710 850 1500 il EJ R a as ae os Error Error Error Error Error Error Error Error COMPARISON OF RESULTS WITH NBS 1 DATA TABLE 4 COMPRESSIBILITY OF CARBON DIOXIDE Temperature Pressure ee From To 0 01am 01 atm dam dam toam atm 40am atm deg K Deg K Avg Max Avg Max Avg Max Avg Max Error Error Error T SS SC a FR m3 e 7 3L BBC NIC 510 e bas foor os fooore na na Ju In DeskTop Gas for Windows Version 4 0 User s Manual Page 30 Chapter 4 Accuracy NA indicates that CO is not in vapor state in this range COMPARISON OF RESULTS WITH ASME 6 DATA TABLE 5 COMPRESSIBILITY OF WATER VAPOR Temperature Pressur
4. NBS data not available COMPARISON OF RESULTS WITH ASME 6 DATA TABLE 10 ENTHALPY OF WATER VAPOR Temperature Pressure Range deg K deg K Avg Max Avg Max Avg Max Error Error Error Error Error Error DeskTop Gas for Windows Version 4 0 User s Manual Chapter 4 Accuracy Page 35 COMPARISON OF RESULTS WITH NBS 1 DATA TABLE 11 ENTROPY OF NITROGEN Temperature Pressure Range egK deg K Avg Max Avg Max Avg Max Error Error Error Error Error Error F 1 1 To 250 oons 0 003 0 009 0 037 0 049 260 D 0 000 0 000 0 001 0 002 0 006 850 0 000 0 000 0 001 0 001 0 002 400 0 000 0 000 0 001 0 001 0 003 500 0 000 0 000 0 001 0 001 0 002 600 0 000 0 000 0 000 0 000 0 001 700 0 000 0 000 0 001 0 001 0 001 800 0 000 0 000 0 000 0 001 0 001 810 1450 Jonge G nge 0 000 0 001 0 001 1500 2000 0 000 0 000 0 000 0 000 0 001 0 001 COMPARISON OF RESULTS WITH NBS 1 DATA TABLE 12 ENTROPY OF OXYGEN Temperature Pressure Range d 80 310 360 410 510 610 710 810 500 pr ag ee ag as af Error Error Error Error Error Error d d S 8 1 80 60 10 60 10 10 10 10 10 500 DeskTop Gas for Windows Version 4 0 User s Manual Chapter 4 Accuracy Page 36 COMPARISON OF RESULTS WITH NBS 1 DATA TABLE 13 ENTROPY OF ARGON Range degK deg K Avg Max Avg Max Avg Max re ter ere rer dr te
5. 024270 oo000a 024271 00000 TABLE 31 Pressure 10 bar 0 078022 0 00015 0 078023 0 000001 0 078022 0 000000 0 11226 0 00017 0 11225 0 00001 0 11225 0 00001 DeskTop Gas for Windows Version 4 0 User s Manual Chapter4 Accuracy Paged TABLE 32 Pressure 50 bar a The differences in saturated humidity ratios between Air or Gas and Hyland amp Wexler can be attributed mostly to the equations used to calculate the pressure of saturated vapor over liquid water Air and Gas use the latest equations provided by IAPWS 7 In the following comparisons the properties calculated by Air and Gas use the saturated humidity ratio as calculated by Hyland amp Wexler in order to show a comparison based on the same composition DeskTop Gas for Windows Version 4 0 User s Manual Chapter 5 DeskTop Gas Error Codes Page 45 5 REFERENCES Tables of Thermal Properties of Gases NBS Circular 564 1955 Vasserman A A Kazavchinskii Ya Z and Rabinovich V A Thermophysical Properties of Air and Air Components Nauka Press Moscow 1966 English translation by Israel Program for Scientific Translations Ltd available from NTIS Springfield Va 1971 as TT70 50095 Rabinovich V A Beketov V G Moist Gases Thermodynamic Properties Begell House Inc New York 1995 Hirschfelder J O Curtiss C F and Bird R B Molecular Theory of Liquids and Gases John Wiley and S
6. by selecting the Print command from either the file menu or the toolbar The tables will include a column for each of the stored points with each of its properties listed in a row A label for each row includes the property name and the current units selected The printing utility will attempt to fit as many points on a page as possible based on the paper size and orientation that you specify using the Print Setup command You can preview the output by selecting the Print Preview command from the File menu 2 9 SAVING AND OPENING DATA FILES When you start DeskTop Gas or open a new file it will be untitled You may save a collection of stored state points along with your selections of units and formats to a DeskTop Gas file Select Save from the File menu or click the disk icon on the toolbar which will open the Save As dialog box You should enter a name for the file the file extension gas will be added automatically You may choose a folder in which to save the file or accept the default folder If you have saved the file at least one time during the session you can save the work under a different filename by choosing the Save As command from the File menu To open a saved file select Open from the File menu or click the open file icon on the toolbar This will open a dialog box that lists all of your DeskTop Gas data files in the current folder You may select a different folder to view other
7. using any of the standard methods for closing Windows applications These include the following e Click the upper left corner of its program window and select close from the menu e Select Exit from the File menu e Press Alt F4 keys e Click the X button in the upper right corner of the program window DeskTop Gas for Windows Version 4 0 User s Manual Chapter 3 Theoretical Basis of Gas Functions Page 16 3 THEORETICAL BASIS OF GAS FUNCTIONS It is commonly accepted that virial equations of state work well for gases In Gas the P V T behavior of a gas mixture is described by a third order virial equation of state B C Rp N RT v y where p Total pressure T Absolute Thermodynamic Temperature v Total volume of gas R Universal Gas Constant B second order virial coefficient of the mixture C third order virial coefficient of the mixture For the ranges of pressure and temperature used in these functions coefficients higher than third order can be ignored It is important to note that Bm and Cm are functions only of temperature Over the range of temperatures and pressures covered by these functions all of the gases except water exist only in the gaseous state Actually CO can exist in a liquid state at the high end of the pressure range and the low end of the temperature range but this state is not considered because it would only occur in a mixture that is almost pure CO At temperatur
8. 022 0 020 0 052 0 0 0 0 egK ss o CH 50 1450 0 009 COMPARISON OF RESULTS WITH NBS 1 DATA TABLE 24 SPECIFIC HEAT OF DRY AIR Range Error Error Error Error Error 25 0 352 3 162 30 0 049 0 382 350 0 020 0 170 400 0 004 0 033 500 0 009 0 056 0 005 0 038 700 0 003 0 022 800 0 005 0 038 50 11450 0 48 1 40 Notes Questionable reference data I CH 5 EH ajn D e A E CO o 0 6 0 S 0 0 6 BE ech 0 0 oO OT ker oa Ojo CO I o DeskTop Gas for Windows Version 4 0 User s Manual Chapter 4 Accuracy Page 42 COMPARISON OF RESULTS WITH HYLAND amp WEXLER 8 SATURATED HUMIDITY RATIO OF MOIST AIR kg of Water Vapor kg of Dry Air TABLE 2 Pressure 1 bar Temp deg C Hyland amp Wexler 0 0 00384 00834 00834 o 1 4833 1 4835 1 4833 TABLE 26 Pressure 5 bar o ooms Tama oorr 9 eme oo a TABLE 27 Pressure 10 bar 0 oom Lies 00002 o pe Jusen 00680 TABLE 28 Pressure 50 bar 0 wes oases ares a mee Tass lass DeskTop Gas for Windows Version 4 0 User s Manual Chapter 4 Accuracy Page 43 COMPARISON OF RESULTS WITH HYLAND amp WEXLER 8 SPECIFIC VOLUME OF SATURATED MOIST AIR m kg of Dry Air TABLE 29 Pressure 1 bar TABLE 30 Pressure 5 bar o Las 000011 06857 00000 ossesr 000000 eo 024273 000015
9. DESKTOP GAS USER S MANUAL VERSION 4 0 COPYRIGHT NOTICE The DeskTop Gas software and manual are copyrighted and licensed for use by one user per copy purchased This manual and the software described in it are copyrighted with all rights reserved Under the copyright laws this manual or the software may not be copied in whole or part without written consent of Techware Engineering Applications Inc Techware Engineering Applications Inc grants permission to the purchaser to make a limited number of copies of the add in for backup purposes only provided that the copies are not in use at the same time as the original Additional reproduction of the software is a violation of copyright law Violators will be prosecuted to the fullest extent of the law Copyright 1997 2002 2009 2012 Techware Engineering Applications Inc All rights reserved DeskTop Gas for Windows Version 4 0 User s Manual 4 TABLE OF CONTENTS INTRODUCTION IEEE 5 1 1 9 Le 5 1 2 32 Bit and 64 Bit VOrsIONS ac ae 5 USING DESKTOP GAS CALCULATOR iini titre ers 6 2 1 NNM 6 2 2 Basic Operation 6 2 2 1 Reference Conditions a ea rei 8 2 3 Re 8 2 4 RUNES be GERNE t 9 2 5 Calculating State Points EE 10 2 6 Formatting Property Valesi naisiin iiie aeeiiaii entre 10 2 7 Labeling and Storing State Points sse eee 11 2 8 San lale PP aa a a A a EE 12 2 9 Saving And Opening Data EE 12 2 10 Advanced L e 12 2 10 1 Expansion Compression Kee IRAN 12 2 10 2 Heat
10. andled properly Comparison of data from Vasserman et al 2 in the temperature range from 850 K to 1300 K supports the conclusion that the tables from NBS 1 are in error Unfortunately the tables from Vasserman et al 2 do not contain data for temperatures above 1300 K Thermodynamic properties for moist air are presented by ASHRAE 10 at atmospheric pressure for temperatures up to 200 deg C The ASHRAE data is based on work done by Hyland and Wexler 8 who provide tables of calculated data at pressures up to 50 bar Comparisons with this data are shown on Tables 29 through 40 Data for Viscosity and Thermal Conductivity is taken from Vasserman et al 2 for the pure gases except for water vapor which is taken from ASME 6 Tables 41 and 42 show excellent DeskTop Gas for Windows Version 4 0 User s Manual Chapter 4 Accuracy Page 28 agreement with this data As with the thermodynamic properties the accuracy of the mixing equations for the transport properties are illustrated by comparison with dry air These comparisons are shown in Table 43 The mixing equations for the transport properties are not as precise as those for the thermodynamic properties however in most cases the errors are less than 1 Some of the table data was generated using the Gas functions for convenience They use the exact same function library as used in DeskTop Gas DeskTop Gas for Windows Version 4 0 User s Manual Chapter 4 Accuracy Page 29
11. be expressed as 2 2 2 2 BynXn BooXo Baatz BecXe 2 D d ByyXyX4 BycXyXc i I l xy Bo XoX4 BocXoXc BacKa c and the second cross virial coefficient of the mixture can be expressed as B Bry Bow o BawXa BewXe 1 ay Similarly the third virial coefficients can be expressed as 3 3 3 3 C wy Xy CoooXo TC aaaXa Cocctc 2 C wo Ko CywaX a CnncXc I 2 C oonXn CooaXa Cooc Xc xo 2 C ccv Xx Ceco o Ceci Xc Ne C 2 A aanXy Ca20 0 TC aachte x ene 888 3 CyocXy XoXc Cac TN X4Xc CojcXoXAXc and 2 2 2 2 C uw Xy CoowXo Caaw XA CecwXc 2 Com SE Tuo oat E i 1 xy CoawXoXa CocwXoXc CacwX aXe DeskTop Gas for Windows Version 4 0 User s Manual Page 17 Chapter 3 Theoretical Basis of Gas Functions Page 18 and Com ET CowwXo T C aw X4 EG ose AT where the subscripts N O A and C refer to N2 O2 Ar and CO respectively Assuming that the condensed phase is pure water the value of Xe can be found by equating the chemical potential of pure condensed water with the chemical potential of its vapor in the gas solution Since the equations describing chemical potentials are non linear and difficult to analyze phase equilibrium is often described in terms of a thermodynamic function called fugacity The equality of chemical potentials can be replaced by equating the logarithms of the fugacity of pure condensed water with that of its vapo
12. cific heat viscosity and thermal conductivity and dew point After recalculation all fields contain property values for the gas mixture at a particular state point 2 2 1 Reference Conditions Enthalpy and entropy values are always expressed relative to particular reference conditions Many people forget that the values of enthalpy and entropy that are found in published tables are not absolute values but instead are relative to particular reference conditions Engineering calculations always deal with enthalpy or entropy differences typically between in flowing and out flowing streams For this reason it does not matter what you select as the reference conditions as long as you use them consistently DeskTop Gas allows you to select reference conditions consistent with ASHRAE or an alternate set of conditions based on absolute zero temperature In SI units ASHRAE uses a reference condition of 0 C and one atmosphere of pressure for dry air For water vapor ASHRAE used a reference condition of liquid water at the triple point temperature of 0 01 C In English units however ASHRAE uses a reference condition of 0 F at one atmosphere of pressure for dry air properties while maintaining the convention of using the triple point as a reference temperature for water properties DeskTop Gas allows you to set the reference temperature of 0 F 0 C or 0 K Please note that in all cases the enthalpy and entropy of the water portion are set to ze
13. ctively If you wish to change the selected property to scientific notation select the Scientific Notation command from the Format menu or press the EE toolbar button The Format menu many be used to change the number format to Fixed Decimal or Percent as well Corresponding toolbar buttons are Fix and respectively Of course the percent format only makes sense for the non dimensional properties The formatting commands are only enabled when the focus is on an IO Box 2 7 LABELING AND STORING STATE POINTS DeskTop Gas gives you the option of labeling and storing any number of state points for future reference After computing the state point DeskTop Gas will automatically suggest a unique name for the new state point such as Point 1 or Point 2 but you will probably want to enter something more descriptive Just enter anew name in the Point Label box To store this point press the Store Point button The Store button will not be enabled if the displayed data is not a correctly calculated state point DeskTop Gas requires all stored points to have a unique label If you try to store two points with the same label DeskTop Gas will query whether you wish to replace the stored point which has the same label with the current point If not you should rename the point and try to store it again After storing the point the state point values for the active point will be copied into a storag
14. e Range 0 01 atm tam dam doam O atm 40am atm Fon fo eman Error Error Error me mes MT men hr eee Lm Bio ooo o 002 0002 poss pss poss ons na Ina COMPARISON OF RESULTS WITH NBS 1 DATA TABLE 6 ENTHALPY OF NITROGEN Temperature Pressure UN From To Ham fioam atm Moa atm deg K Ideg K Avg Max Avg Max Avg Max Error Error Error A Error Error S ner one ha ka res ee jn poor haha pes ons ae po re pore pan pros poor bebe 210 pue for poris oan ooo porc poros DeskTop Gas for Windows Version 4 0 User s Manual Page 31 Chapter 4 Accuracy Page 32 SCC _ Jpooox anre poor oss ooo aos DeskTop Gas for Windows Version 4 0 User s Manual Chapter 4 Accuracy COMPARISON OF RESULTS WITH NBS 1 DATA TABLE 7 ENTHALPY OF OXYGEN Range deg K deg K Avg Max Avg Max Avg Max re ter cree rer der te COMPARISON OF RESULTS WITH NBS 1 DATA TABLE 8 ENTHALPY OF ARGON Temperature Pressure Range eg K deg K Avg Max Avg Max Avg Max Error Error Error Error Error Error 180 Pen 0 049 0 376 0 082 0 529 0 075 0 199 DeskTop Gas for Windows Version 4 0 User s Manual Page 33 Chapter 4 Accuracy Page 34 COMPARISON OF RESULTS WITH NBS 1 DATA TABLE 9 ENTHALPY OF CARBON DIOXIDE Range egK deg K Avg Max Avg Max Avg Max Error Error Error Error Error Error 260 800 o 019 0 030 0 023 0 057 NA 10 850 o 014 0 021 0 049 0 064 0 389 0 864
15. e array and given the name you selected The point will be displayed in the stored points column in same units as the active point After a state point is stored its name is added to the point name combo box in the upper right hand corner of the main window You can view a stored point by pressing the arrow on the point name combo box and selecting a point from the drop down list If you wish to use a stored point with any of the special tools or as the basis for calculating a new point you must recall the stored point to the active point Begin by selecting the point from the point name combo box s dropdown list Next press the Recall Point button to copy the stored point to the active point You may now use the active point for new calculations If you change any input data and press Compute the active point will be changed but the stored point from which you copied the values will remain intact You can delete a stored point by first selecting it from the Point Name combo box and then select Delete Point from the Edit menu This collection of state points can be saved as a DeskTop Gas file In addition you can copy state points to the clipboard where they can be transferred to another application such as a spreadsheet program or word processor DeskTop Gas for Windows Version 4 0 User s Manual Chapter 2 Using DeskTop Gas Calculator Page 12 2 8 PRINTING You can print a table consisting of all of the stored points
16. e values will be converted to the new units and you will have to re enter them The first time the program is started the properties will be displayed in SI units You can change all of the units to either standard English or SI units by issuing the English Units or SI Units command from the Format menu or pressing the Eng or SI toolbar button When you change to English units in this manner the reference temperature for the dry gas is changed to 0 F Similarly when changing to SI units the reference temperature is changed to 0 C If you change the units one at a time the reference temperature will not change even if you change all of the units from English to SI units You can force a change in the reference temperature by pressing the Ref button on the toolbar or by selecting Options from the Tools menu and then choosing the Reference Point tab From either of the dialog boxes you will be able to select the desired reference temperature You may choose any combination of available units for your personal default unit set Simply select the units you desire for each property and issue the Make Current Settings Default command from the Format menu The next time you start DeskTop Gas your default unit set will be used If you change units and then save a file those selected units will be restored whenever the file is opened If you wish to change the units back to your default unit set issue
17. ealing with processes that involve evaporation or condensation of water vapor If you want the mass dependent properties to be expressed on a wet basis instead of a dry basis press the button labeled Change to per Wet Mass Next select the input properties by selecting the corresponding check boxes as described above Enter values for those properties in the boxes to the right of the property names The next section describes various methods for entering data When you enter a value for any of the key properties a red X appears next to the property value to indicate that a new value has been entered This is a warning that the value being displayed is not consistent with the current state point After a compute command is completed successfully all property values are recalculated and the red X s are cleared Be sure to enter the values in units consistent with the unit displayed to the right of the value box If you wish to change units select the desired units before entering the value If you change units after the value is entered the value entered will be converted to the new units DeskTop Gas for Windows Version 4 0 User s Manual Page 7 Chapter 2 Using DeskTop Gas Calculator Next click the Compute button to find all the unknown properties If the Compute button is grayed you have not checked enough properties to define the state point Fields without check boxes are output only These include spe
18. er s Manual Page 8 Chapter 2 Using DeskTop Gas Calculator The IO Box has two modes of operation input and output When new data is entered the IO Box is placed in the input mode and a red X appears to the left of the box After a new state point is computed all IO Boxes are placed in the output mode and the red X s are removed The IO Box accepts either numerical values or arithmetic expressions that can be evaluated to a numeric value A number can be entered in either decimal or scientific notation The expression can be any valid arithmetic expression using the following operators add subtract multiply divide i exponent parentheses Arithmetic calculations can be nested to any level using parentheses An example of a valid expression is 1004 2 997 2 2 5 which evaluates to 1000 506 Expressions are evaluated whenever you tab to or click on another control or press the Enter button Only the resulting value is shown in the box If you enter an incorrect expression your computer will beep and the edit cursor will highlight the offending character You must fix the error before DeskTop Gas will allow you to continue If the expression you are entering is too long to fit in the box the box will temporarily increase in length so that you may view more of the expression When you are finished editing the box returns to its original length To recall the last expression used in an input box u
19. erties when a state point is defined by known properties The program is flexible and designed to minimize keystrokes for common calculations DeskTop Gas allows you to enter any number of state points label tnem and store the collection of points for later reference You can print a table of stored points or copy them to the clipboard and paste them into your favorite spreadsheet or word processor Major features of this program include validity over a wide range of pressures and temperatures flexible interactive design large choice of units for each property tools for heating cooling expansion and compression processes instant response time extensive help screens O 20 0 00 0 0 If installed properly DeskTop Gas is started by simply double clicking on its name icon in the DeskTop Gas subgroup of the TechwareEng Group appearing on the Windows Start Menu 2 2 BASIC OPERATION The DeskTop Gas display is arranged in a tabular format that remains constant although the program window can be re sized You may sometimes find it convenient to make the program window smaller Each of the rows in the top section is dedicated to one of the gas properties pressure temperature specific volume enthalpy entropy specific heat dynamic viscosity thermal conductivity and dew point temperature Each of the rows in the Gas Composition section shows the fraction of one of the individual gasses as well as the humidity ratio and molecular weig
20. es where the saturation pressure of pure water is greater than the total gas pressure the mole fraction of water vapor can range from 0 to 1 That is there is no limit to the percentage of water vapor in the gas mixture in that situation Elsewhere the mole fraction of water vapor can range from 0 to a limiting saturated value xeq which is reached when the condensed phase of water is in thermodynamic equilibrium with the gas solution This equilibrium fraction is equivalent to the solubility of the condensed water in the solvent gas mixture In order to facilitate calculation of Xeq it is convenient to group the virial coefficients of the non water gases so that the mixture can be treated as a binary mixture between the non water gases and water vapor The virial coefficients of the gas mixture can be expressed as aia 2 B X B 2 x D LY B gw gw wo ww and DeskTop Gas for Windows Version 4 0 User s Manual Chapter 3 Theoretical Basis of Gas Functions C x C 3x2x C 3x x C EC 87888 ggw net Xw www where Wi mole fraction of the non water gases in mixture x mole fraction of water vapor in the mixture B C virial coefficients of the non water gases By Cum Virial coefficients of water vapor www Boys Cyan Coy cross virial coefficients Since the sum of the mole fractions of the mixture must equal 1 the value xg is equal to 1 xy The second virial coefficient of the non water gases can
21. files Select the file you want to open and press the Open button to load the file To start a new file select the New button from the Toolbar If you have stored any points and have not saved the file you will be prompted to do so 2 10 ADVANCED FEATURES DeskTop Gas includes special tools that facilitate the calculation of some common gas processes These tools include an Expansion Compression tool and a Heating Cooling tool 2 10 1 Expansion Compression Tool The Expansion Compression tool is used to evaluate performance of a gas turbine or an gas compressor If you are predicting the performance and know the efficiency of the turbine or compressor the tool can be used to calculate the state point conditions at the expansion or compression end point If you are analyzing the performance of a turbine or compressor and know the conditions at the end point the tool can be used to calculate the efficiency The tool also computes the energy converted to shaft work generated by the turbine or used by the compressor DeskTop Gas for Windows Version 4 0 User s Manual Chapter 2 Using DeskTop Gas Calculator Page 13 To use the tool first select the active state point representing the start of the expansion or compression path Next select Expand Compress from the Tools menu or click the turbine icon on the toolbar which will open the Expansion Compression tool dialog box In the tool dialog box select the conditions you wi
22. g gas properties This method is accessed using the Copy Point command on the Edit menu Regardless of whether any text is selected this command copies a table of text values to the clipboard using either the Active Point or all of the stored points The table includes one column for each point You can optionally direct DeskTop Gas to also include property and unit labels in which case they DeskTop Gas for Windows Version 4 0 User s Manual Chapter 2 Using DeskTop Gas Calculator Page 15 appear as the first column in the table The table includes one row for each property in the same order as they are displayed on DeskTop Gas main window All values are copied to the clipboard using the same format displayed on the screen So if you need more accuracy in your Excel calculations set the DeskTop Gas display accuracy accordingly before issuing the Copy Point command 2 11 GETTING HELP The Help menu offers extensive on line help for DeskTop Gas The About item in the Help menu presents the version and serial numbers of your copy of Gas If the program is running in its Demo mode the number of days remaining on the Demo are displayed instead of a serial number 2 12 ERROR MESSAGES When input values are out of range or any other errors occur a message box is displayed describing the error The calculated fields will not be updated until the error condition is resolved 2 13 EXITING DESKTOP GAS You may exit DeskTop Gas by
23. gas flow rate that you entered The units for these results will be consistent with your input units You may change any of the data and repeat the calculation as required When you are satisfied with the result you may copy that state point back to the Active Point on DeskTop Gas main window by pressing the Close and Copy to Current Point button Note that the values for moist gas in the second column will be copied back to the active point If no condensation has occurred these values will be the same as in the first column labeled mixture If condensation has occurred then the values in the second column will be at saturated conditions If you do not wish to replace the Active Point on the main window with the heating cooling state point calculated just press the Cancel button 2 10 3 Exchanging Data with Other Programs DeskTop Gas includes two ways to share data with other applications running on your PC such as Excel Both methods use the Windows clipboard In the first data sharing method DeskTop Gas Edit Copy command copies whatever text is highlighted in an IO Box e g a number or part of a number to the Windows clipboard From there that text can be pasted into other applications running on your PC This is typically done using those applications Edit Paste command The second data sharing method also places text on the clipboard but uses an extended format that is especially useful for calculations involvin
24. h the first selected property You may change your selections by un checking one or all of the check boxes and selecting a new combination To compute a gas property state point begin by entering the gas composition in the lower half of the calculator If you wish to use the composition for standard dry air press the button labeled Set to Standard Dry Air Note the label in the units column next to each gas component It indicates the basis of the gas composition Initially the label should indicate Vol frac Dry which means that the gas composition is entered as a volume or mole fraction on a dry basis Note that the value for water vapor is zero and the box is read only This ensures that you can only enter water vapor as a humidity ratio If you want to enter the composition on a wet basis press the button labeled Change to Wet Composition Now you will find that the humidity ratio is read only and water vapor box is enabled If you want to enter the composition as mass fractions instead of mole fractions press the button labeled Change to Mass Fraction The other button in the gas composition section resets the gas composition to all zeros All mass dependent properties specific volume enthalpy entropy specific heat and viscosity can be expressed on either a dry or wet basis The default for DeskTop Gas expresses the properties per mass of dry air This is consistent with ASHRAE conventions and is quite useful when d
25. he calculation as required When you are satisfied with the result you may copy that state point back to the active point on DeskTop Gas main window by pressing the Close and Copy to Current Point button Note that the values of moist gas in the second column will be copied back to the active point If no condensation has occurred these values will be the same as in the first column labeled mixture If condensation has occurred then the values in the second column will be at saturated conditions If you do not wish to replace the current point on the main window with the expansion end point calculated just press the Cancel button 2 10 2 Heating Cooling Tool The Heating Cooling tool is used to analyze a gas stream in which heat is either added or removed If you know the quantity of heat that is being added to or removed from the gas stream you can use the tool to calculate the resulting state point temperature and other conditions If you know the temperature or enthalpy of the gas leaving the heating or cooling device you can use the tool to calculate the quantity of heat exchanged To use the tool first make sure that the active state point represents the conditions of the gas entering the heating or cooling device Next select Heat Cool from the Tools menu or click the flame icon on the toolbar which will open the Heating Cooling tool dialog box DeskTop Gas for Windows Version 4 0 User s Manual Chapter 2 Using DeskTo
26. ht of the mixture There is a column that displays the property values for the active point and a column that displays data for one of the stored points The key properties that can be used to define the gas state point are pressure temperature specific volume enthalpy entropy and the gas composition Theoretically a state point can be uniquely identified by specifying the gas composition and any two of the other five DeskTop Gas for Windows Version 4 0 User s Manual Page 6 Chapter 2 Using DeskTop Gas Calculator properties In most practical applications pressure is usually one of the known variables Most of the calculations require that the pressure be known In the rare case when pressure is not known it can be calculated from the equation of state if the dry bulb temperature and specific volume are known Each of the key properties has a check box associated with it When checked it signifies that this property is to be used in calculating the state point In general two thermodynamic properties and the gas composition must be selected before DeskTop Gas will allow a computation If pressure and temperature are selected DeskTop Gas can compute the gas properties in the state that is saturated with water vapor In these cases you will notice that the Compute Saturated button is enabled Once you select one property DeskTop Gas will disable all the other check boxes whose properties are not allowed in combination wit
27. ing Cooling E EE 12 2 10 8 Exchanging Data with Other brogorams sss eee eee 14 2 11 Getting Hensel 15 2 12 Err rIMessages nie eek se ee 15 2 13 Exiting DeskTop EE 15 THEORETICAL BASIS OF GAS FUNCTIONS sse eee 16 3 1 Gas Property Database reo iic rame mE aaa 19 3 2 Computational Model toit eio RER atto aieo d 21 3 3 Transport Properties ende de nennen su nde ken 21 DeskTop Gas for Windows Version 4 0 User s Manual 4 5 4 1 3 3 1 Ve eT T 332 Uerteel ACCURACY Accuracy of Calculations sss REFERENCES DeskTop Gas for Windows Version 4 0 User s Manual Chapter 2 Using the DeskTop Gas Property Functions Page 5 1 INTRODUCTION 1 1 OVERVIEW DeskTop Gas is an interactive gas property calculator that provides thermodynamic and transport properties for mixtures of moist gases The current library includes the following gases nitrogen N2 oxygen O2 argon Ar carbon dioxide CO2 and water vapor H2O The thermodynamic property functions are calculated for mixtures of all five gases using an accurate third order virial equation of state See the theory and accuracy section for an explanation of how Techware developed the equation of state These five gases account for 99 997 of the volumetric composition of standard air and also account for better than 99 9 of most combustion gases The functions are valid over a temperature range from 180 K 136 F to 2000 K 3140 F and at pressures
28. ll use to compute the end point from the combo box near the top of the screen Select Pressure amp Efficiency if you know the pressure and efficiency If you are checking an actual machine you will need to know the exiting gas temperature or enthalpy Check either the Pressure Enthalpy or Pressure Temperature buttons as required The two variables you have chosen will have their value fields enabled all others will be grayed Enter the appropriate values and click the Compute button The Gas Flow In column displays the state point properties entering the equipment which were copied from the active point The Total Flow Out box has three columns that display the state point properties at the end of the expansion The first column identifies the thermodynamic properties for the moist gas mixture and liquid water if any exiting the equipment The second column displays the thermodynamic properties for the moist gas exiting and the third column shows the properties for the liquid water if any condensation occurs The units displayed are those currently in use on DeskTop Gas main window If you wish to use different units you should select those units on the main window before opening the expansion tool Below the state point properties you will find the shaft power based on the entering gas flow rate that you entered The units for these results will be consistent with your input units You may change any of the data and repeat t
29. n reference 1 B and C virial coefficients for the pure gases were obtained by using a least square fit of the compressibility function to isotherms at 10 degree increments from 180 K to 800 K and at 50 degree increments from 800 K to 2000 K Mixed virial coefficients were calculated from molecular theory using the Leonard Jones 6 12 potential model The following equations were used to calculate the virial coefficients based on the model B r QaN 13 o B T y r QzN 13 og C T iij C j r QzN 13 06c T ij C ij where N 6 02205E per mole Avogadro s number T kTle or T KTle or T kT 8 k 1 3807E J K Boltzmann constant The equations and constants for calculating B and C are found in Hirshfelder Curtis and Bird 4 Values of potential parameters o and ck for the pure gases were obtained by minimizing the errors in predicting the compressibility factors of the pure gases using the Leonard Jones 6 12 potential Mixed potential parameters were obtained by means of the following semi empirical mixing rules On 03 0 tOn EN e k lelk lelk 12 O15 d 0 07 Oin d 0 e Leit S leit lerk Lei ei Kale KI Where DeskTop Gas for Windows Version 4 0 User s Manual Chapter 3 Theoretical Basis of Gas Functions Page 21 b 14 0892 3a 17 Ven ker 2aN o when gas 1 is non water and gas 2 is water or amp 1 0 when both gases a
30. nd high pressures This is due to the limitations of using a third order virial equation of state There is little published data on the properties of mixed gases One method to illustrate the accuracy of the mixing equations is to compare the results of DeskTop Gas to data for dry air which is a mixture of Nitrogen Oxygen Argon and a small amount of Carbon Dioxide Tables 21 through 24 show the comparison with air for the thermodynamic properties As with the pure components small errors can be observed at low temperatures and high pressures due to the limitations of the model The tables show some differences in enthalpy entropy and specific heat occurring at 850 K and growing with temperature This initially was thought to be attributed to dissociation but this was dismissed for two reasons First dissociation effects were not included below 1500 K in reference 1 Second the error is much greater than what can be attributed to dissociation above 1500 K Further examination of the data tables suggests that the tables in reference 1 are in error One would expect the thermodynamic properties to approach the ideal gas properties as the pressure is reduced to zero While this is the case for temperatures up to 800 K it is not the case above 800 K Curiously at 800 K the tables in reference 1 change from a temperature increment of 10 K to 50 K at the point where the error begins Perhaps this change of temperature increment was not h
31. ons 1954 Mangum B W and Furukawa G T Guidelines for Realizing the International Temperature Scale of 1990 ITS 90 NIST Technical Note 1265 1990 6 Thermodynamic and Transport Properties of Steam ASME New York NY 1993 The IAPWS Formulation 1995 for the Thermodynamic Properties of Ordinary Water Substance for General and Scientific Use International Association for the Properties of Water and Steam Paris France September 1995 R W Hyland A Wexler 1983 Formulations for the Thermodynamic Properties of Dry Air from 173 15 K to 473 15 K and of Saturated Moist Air from 173 25 K to 372 15 K at Pressures to 5 MPa ASHRAE Transactions 89 2A 520 35 Robert C Reid John M Prausnitz Bruce E Poling The Properties of Gases and Liquids Fourth Edition McGraw Hill Inc American Society of Heating Refrigeration and Air Conditioning Engineers ASHRAE Fundamentals 1993 DeskTop Gas for Windows Version 4 0 User s Manual
32. ons Page 25 The equation for thermal conductivity of the moist gases is as follows EE 1 Z where thermal conductivity of the mixture X lt or 2 2 y ty p eke yO Fey 8 ow w 2 de NO M 10M M SS 12 12 15 77 1508 M 2 MM w 0 4 1 12 ANM 1M M 3 Utt ae al 2 Bo dq ee dee 15 2 EA M 2 MM 8 Usa d A Pa 5 12 d pue 13 MM JAA 33S MM 4 M M YA Au 1012 PE Bi 1 15 4MM J A 12 5 A Thermal conductivity of dry gas mixture at the specified temperature Thermal conductivity of water vapor at the specified temperature Tim M 2M M Fea To gw A Cy gw and C 1989 1E 7 Bj function of reduced temperature DeskTop Gas for Windows Version 4 0 User s Manual Chapter 3 Theoretical Basis of Gas Functions Page 26 To correct for pressure we use the Stiel and Thodos modification as described in Reid Prausnitz and Poling 9 DeskTop Gas for Windows Version 4 0 User s Manual Chapter 4 Accuracy Page 27 4 ACCURACY 4 1 ACCURACY OF CALCULATIONS Thermodynamic properties for the pure gases calculated by DeskTop Gas have been checked against the values published by NBS 1 and ASME 6 for water vapor As shown on Tables 1 through 20 the calculated values show excellent agreement with the source data throughout most of the valid range Some small differences can be observed at low temperatures a
33. p Gas Calculator Page 14 In the tool dialog box select the conditions you will use to compute the end point from the combo box near the top of the screen Select Pressure Heat Flow if you know the pressure and heat added or removed If you are measuring performance on an existing device you will need to know the exiting gas temperature or enthalpy Check either of the Pressure Enthalpy or Pressure Temperature buttons as required The two variables you have chosen will have their value fields enabled all others will be grayed Enter the appropriate values and click the Compute button The Gas Flow In column displays the state point properties entering the equipment which were copied from the Active Point in the main screen window The Total Flow Out box has three columns that display the state point properties at the end of the expansion The first column identifies the thermodynamic properties for the mixture of moist gas and liquid water exiting the equipment The second column displays the thermodynamic properties for the moist gas exiting and the third column shows the properties for the liquid water if any condensation occurs The units displayed are those currently in use on DeskTop Gas s main window If you wish to use different units you should select those units on the main window before opening the Heating Cooling tool Below the state point properties you will find the heat added based on the entering
34. r Error Error 180 250 0 031 0 093 0 517 1 643 1 574 4 829 DeskTop Gas for Windows Version 4 0 User s Manual Chapter 4 Accuracy COMPARISON OF RESULTS WITH NBS 1 DATA TABLE 19 SPECIFIC HEAT OF CARBON DIOXIDE Range Error Error Error Error Error Error NBS data not available COMPARISON OF RESULTS WITH ASME 6 DATA TABLE 20 SPECIFIC HEAT OF WATER VAPOR Temperature Pressure Range egK degK Avg Max Avg Max Avg Max Error Error Error Error Error Error 10 zoo l0 065 0 080 0 045 0 075 0 146 0 302 710 g00 0 093 0 106 0 093 0 119 0 087 0 154 DeskTop Gas for Windows Version 4 0 User s Manual Page 39 Chapter 4 Accuracy Page 40 COMPARISON OF RESULTS WITH NBS 1 DATA TABLE 21 COMPRESSIBILITY OF DRY AIR Temperature Pressure a From To oam 01 atm am O dam toam O atm 4am O atm ST Error Error Error Error Error Error Error Error SO O ores foor ooo Jooris fora COMPARISON OF RESULTS WITH NBS 1 DATA TABLE 22 ENTHALPY OF DRY AIR Temperature Pressure mu From To fam fam oam atm 40am atm release Error Error Error Error Error Error 510 Ja ko O oos fons poor DeskTop Gas for Windows Version 4 0 User s Manual Chapter 4 Accuracy Page 41 COMPARISON OF RESULTS WITH NBS 1 DATA TABLE 23 ENTROPY OF DRY AIR Range degK Avg Max Avg Max Avg Max Error Error Error Error Error Error 8 250 0 002 0 003 0 006 0
35. r in the gas mixture solution The equation of solubility based on this concept is derived by Rabinovich 3 and can be expressed as follows kap dans dp Bo In Se In lern RT E V weona AP e DE ce GES Cas Prag 2 2 ve re he I e cac ec h ggw gww eq where B C IE z 1 the compressibility of the gas mixture or the water vapor as required V V p saturation pressure of water vapor at temperature T y the volume of the condensed water wcond The solubility equation can be solved for Xeq by iteration For an ideal solution Xegideal is equal to the ratio of the vapor pressure of the pure water to the total pressure of the mixture The ratio Of Xeq Xegideal IS called the enhancement factor or excess solubility and has a value greater than 1 The value of Xe is used to find the dew point temperature of a gas mixture to determine the amount of condensation that occurs in a cooling process and to verify that the value of x input by the user does not exceed xe The thermodynamic properties enthalpy entropy and specific heat at constant pressure can be determined from knowledge of the properties in the ideal gas state and the virial coefficients The molar enthalpy of a moist gas mixture hm can be described by the equation h Xy hs hy xo h5 ho x h h e xc h2 the DeskTop Gas for Windows Version 4 0 User s Manual Chapter 3 Theoretical Basis of Gas Functions Page 19 dear REE OB i
36. re non water and i polarizability of the apolar molecules t 8 uleo u dipole moment of the molecule Some of the mixed potential parameters between No Ar and CO with water were determined by Rabinovich 3 based on experimental data on the equilibrium fractional content of water vapor in the solvent gas Where available these mixed potential parameters were used instead of the ones derived from the mixing rules Based on the methods described a database was developed containing all of the pure gas and mixed virial coefficients for the five gases at 10 degree increments from 180 K to 800 K and at 50 degree increments between 800 K and 2000 K A similar database was developed for the ideal gas enthalpies entropies and specific heats 3 2 COMPUTATIONAL MODEL With most of the functions the mixture s pressure and temperature are known Since the virial coefficients are functions only of temperature the database is used to calculate mixed coefficients Boo Bow Bww Logg Cogw Cgww and Cwww based on the formulas identified above at four temperatures surrounding the desired temperature Four point non linear interpolation is used to calculate the mixed coefficients and their derivatives at the desired temperature Since most of the properties require knowledge of the specific volume of the mixture the virial equation of state is used iteratively to calculate the specific volume In cases where the temperature of the mixture is no
37. ro for liquid water at the triple point Some publications which are based on perfect gas assumptions assign the zero point for enthalpy and entropy to water in the vapor state at the triple point or some other specified temperature We believe that setting the zero point for enthalpy and entropy to water in the liquid state rather than in the vapor state has two major advantages First the values are numerically equivalent to standard international steam tables and Techware s WinSteam product This facilitates the handling of processes that include both moist gas and liquid water streams without worrying about reference temperatures Second It greatly simplifies analysis of processes in which water is either condensed from or evaporated to the gas stream All of DeskTop Gas reference conditions use the International Temperature Scale of 1990 ITS 90 as the basis of temperature 2 3 ENTERING DATA Numeric data is entered in a specially designed edit box called an IO Box which behaves like a standard Windows edit box but includes some additional features To enter new data double click the IO Box and all the data will be highlighted As you enter new data the old data will be replaced To edit data hold the left mouse button down and drag the mouse over the characters that you wish to replace thereby highlighting them Release the mouse button and type new characters to replace the highlighted ones DeskTop Gas for Windows Version 4 0 Us
38. se the Recall Expression command on the Edit menu You ll then have the opportunity to edit the expression and let the IO Box re evaluate it Note that the box retains the last number or expression entered even after a compute command is issued As a result the value in the box will not reflect the value of the recalled expression if a compute command has altered the value You may use the Cut Copy and Paste commands on the Edit menu or the toolbar to exchange numeric data between DeskTop Gas IO Boxes and any other application that supports the clipboard If you start entering data in an IO Box and wish to go back to the original data you may use the Undo command on the Edit menu However once the IO Box loses the focus the Undo command is no longer available 2 4 UNIT SELECTION DeskTop Gas allows you to use any combination of units for input and output properties The units for each property can be set independently by using its associated combo box To DeskTop Gas for Windows Version 4 0 User s Manual Page 9 Chapter 2 Using DeskTop Gas Calculator Page 10 change a unit select its combo box and scroll through the list of available units using either the keyboard cursor arrows or the mouse Whenever a new unit is selected the program converts the values displayed for that property to the new units Therefore when entering data you should first select the units and then key in the input values Otherwise th
39. t xy hy hy NU NGT y where h ideal gas molar enthalpy for gas i h constant to adjust reference state for gas i The molar entropy of the moist gas mixture Sm can be described by the equation e x s s Ali TAn x s s Er xc 82 ak sz sy RInp E ae An 7 E Es E os e een s T E be T 3 X RT KR xy RT v OT j 2v OT where s ideal gas molar entropy for gas i s constant to adjust reference state for gas i The molar specific heat at constant pressure of a moist gas mixture Cm can be described by the equation RT B eB RT X GC m6 E E FCU eg EE FR c T d E T m j4 v OT PG 2y Or or B C TB TOC R 1 et vv vc v amp ZB BC E EE V V where c ideal gas molar specific heat at constant pressure for gas i U 3 1 GAS PROPERTY DATABASE In order to use the equations presented in the previous section to calculate the thermodynamic properties it is necessary to know the B and C virial coefficients of each of the pure gas DeskTop Gas for Windows Version 4 0 User s Manual Chapter 3 Theoretical Basis of Gas Functions Page 20 components and the mixed virial coefficients for all mixture combinations In addition the ideal gas enthalpies entropies and specific heats are required for each gas component Tables of compressibility data for the pure gases and the ideal gas enthalpies entropies and specific heats are provided i
40. t known iterative procedures are used to determine the temperature as well 3 3 TRANSPORT PROPERTIES Values for viscosity and thermal conductivity of individual gases at atmospheric pressure can be found in many references although there does not appear to be any definitive standard of accepted values as there are for steam and water We found the most complete coverage by Vasserman Kazavchinskii and Rabinovich 2 who have surveyed the available literature and presented tables of values over a range of temperatures and pressures We have used their DeskTop Gas for Windows Version 4 0 User s Manual Chapter 3 Theoretical Basis of Gas Functions Page 22 tabular values of viscosity and thermal conductivity as the basis of our database for Nitrogen Oxygen Argon and Carbon Dioxide We have used the equations recommended by ASME 6 to compute the viscosity and thermal conductivity properties for water vapor These are the same equations used in our WinSteam product There is little information available regarding the viscosity and conductivity of moist gases In most practical cases the relatively small quantity of water vapor in gas mixtures has a small effect on the overall transport properties unlike the thermodynamic properties which are greatly affected by moisture Nonetheless we have selected a method to account for the effects of moisture on viscosity based on kinetic theory as presented by Hirshfelder Curtis and Bird 4
41. the command Restore Default Settings from the Format menu 2 5 CALCULATING STATE POINTS When you have finished entering values for the selected input variables click the on screen button labeled Compute to calculate all of the state point properties If the Compute button is grayed you have not checked enough properties to define the state point You may also compute the state point by pressing the Enter key on your keyboard Note that the Enter key serves two purposes in DeskTop Gas Pressing the Enter key just after entering data in an IO Box tells DeskTop Gas to evaluate the expression in the IO Box Pressing the Enter key a second time tells DeskTop Gas to compute the state point If you move the focus to any other control after entering data in an IO Box the expression is evaluated automatically and you only have to press the Enter key only once to compute the state point The Enter key will not compute a state point if the Compute button is grayed 2 6 FORMATTING PROPERTY VALUES DeskTop Gas normally displays all property values in fixed decimal notation You may increase or decrease the number of decimal places in a selected property IO Box by selecting DeskTop Gas for Windows Version 4 0 User s Manual Chapter 2 Using DeskTop Gas Calculator Page 11 Add Decimal Places or Decrease Decimal Places from the Format menu or by clicking 0 00 either of the sa 5 toolbar buttons respe
42. up to 50 bar 725 psia DeskTop Gas can be used to calculate the thermodynamic and transport properties of moist air by using the composition of standard air In some cases when dealing with psychrometric properties of air such as relative humidity wet bulb temperature or degree of saturation it may be more convenient to use Techware s DeskTop Air add in which includes properties to handle these parameters The two packages use similar equations except that the DeskTop Air program mixes two gases dry air plus moisture while the DeskTop Gas product mixes five discrete gases Nonetheless the values returned by DeskTop Gas when using a mixture composition corresponding to standard dry air agree quite well with those returned by the DeskTop Air 1 2 32 BIT AND 64 BIT VERSIONS The DeskTop Gas package includes both 32 bit and 64 bit installation files If you are running a 64 bit operating system such as Windows 7 you should install the 64 bit version otherwise you should install the 32 bit version They are functionally identical DeskTop Gas for Windows Version 4 0 User s Manual Chapter 2 Using DeskTop Gas Calculator 2 USING DESKTOP GAS CALCULATOR 2 1 OVERVIEW DeskTop Gas is a Windows application which calculates the thermodynamic and transport properties of a mixture of moist gases It can be used as an interactive replacement for gas property tables but does much more than that It automatically calculates all unknown prop
43. viscosity of dry gas mixture at the specified temperature 7 viscosity of water vapor at the specified temperature DeskTop Gas for Windows Version 4 0 User s Manual Chapter 3 Theoretical Basis of Gas Functions 2M M TIM M C 1 gw 1 c oer gw 12 gw and C1 266 93E 7 6 7 potential function parameter for mixture adjusted for one polar molecule M weighted average molecular mass of the dry gas mixture Page 24 To correct for pressure we use the method of Chung et al as described in Reid Prausnitz and Poling 9 3 3 2 Thermal Conductivity In a similar manner to calculate thermal conductivity we treat the gas as a binary mixture of the non polar gases and water vapor For the non polar gas mixture we use the Wassiljewa equation with the Mason and Saxena modification described by Reid Prausnitz and Poling 9 xA l e i_ where DA j l H A thermal conductivity of the gas mixture A thermal conductivity of component i x x mole fraction of components i and j i J Aj 1 0 12 14 p tri ay M M 4 ESCE GR bo vu value that varies from 0 9 to 1 05 as a function of temperature uu exp 0 04647 exp 0 24127 Ano tr T exp 0 04647 exp 24127 TM 1 6 SE c G T P critical temperature and pressure DeskTop Gas for Windows Version 4 0 User s Manual Chapter 3 Theoretical Basis of Gas Functi
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