InfoGet PsychedPsychrometric Worksheetver 2.0focus on energy

&L(C) Copyright 1998. All rights reserved by KW Energy Engineering.This sheet will allow you to do psychrometric calculations in Excel and plot your results on a psych chart. The spreadsheet formulas are based on ASHRAE correlations and are accurate to more decimal places than you can read off a psych chart.

OverviewThe Get Psyched software includes two basic parts:

1) The Add-In (PSYCH.XLA)The add-in allows you to do psychrometric calculations in any Excel spreadsheet. After you have installed the add-in you can use psychrometric functions in calculations just like you use other functions in Excel. For more information on how to use the functions, see the help file.

2) The Spreadsheet Template (PSYCH.XLT & PSYCH_SI.XLT)The spreadsheet template (this file) uses the add-in functions to create a psychrometric chart. The chart can be easily customized for any altitude. The template also includes some example calculations and an easy method for adding your own data to the psych chart. You can use the spreadsheet template as a starting point for your own spreadsheets. For more information on how to use the template, see the help file. The template is available in IP units (PSYCH.XLT) and metric (SI) units (PSYCH_SI.XLT).

These are the properties that you can calculate with the Psychrometric Function Library:

Enthalpy [Btu/lb] Dewpoint Temperature [F] Relative Humidity [%] Humidity Ratio [lbs H2O per lb dry air or grains] Specific Volume [ft^3 per lb] Wet Bulb Temperature [F]SOFTWARE LICENSE AGREEMENT

This is an agreement between you, the end user, and kW Engineering ("KW"). By using this software, you are agreeing to become bound by the terms of this agreement.IF YOU DO NOT AGREE TO THE TERMS OF THIS AGREEMENT, DO NOT USE THIS SOFTWARE. PROMPTLY RETURN THE ENTIRE PACKAGE TO THE PLACE WHERE YOU OBTAINED IT.

1. GRANT OF LICENSE. KW, as Licensor, grants to you, the Licensee, a non-exclusive right to use this software program (hereinafter the "Software") in accordance with the terms contained in this license. You may use the Software on a single computer free of charge for a period of 60 days from the date you install it. If you wish to use the Software on more than one computer, you must either erase the software from the first computer when you move the Software to another computer, or else purchase two copies of the Software. You may execute the Software from a common disk shared by multiple computers provided that one authorized copy of the Software has been licensed for each computer executing the Software.

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6. This License shall be governed and construed in accordance with the laws of the Sate of California and shall benefit KW Engineering, its successors and assigns.This workbook contains all of the elements necessary to create a customized psychrometric chart for any altitude up to 30,000 ft. The following is a brief summary of the sheets in it. Detailed directions are on the sheets.

Info: General information and instructions Sheet1: Sets the altitude and resulting pressure for calculations Examples: Shows how the functions are used Data to Graph: Tables to plot data on the psychrometric chart Psych Chart: The psychrometric chart Plot Data (Hidden): Used to plot enthalpy and relative humidity lines on the chart

Don't delete Sheet1 from the workbook if you want to use the psych chart. Rename it instead. Sheet1 holds the value for the pressure at which the calculations are done for plotting enthalpy and relative humidity lines on the chart.The functions are all based on correlations published in the 1997 ASHRAE Handbook of Fundamentals. According to ASHRAE "these relations are sufficiently accurate for most engineering calculations in air-conditioning practice..." Refer to Fundamentals, Chapter 6, under the heading "Numerical Calculation of Moist Air Properties" for more details.

There is some discrepancy among the functions in the evaluation of humidity ratio and and relative humidity at low humidities and low temperatures. The properties calculated using dew point as a state variable do not agree precisely with quantities calculated using wet bulb temperature or relative humidity (which agree with each other very closely). The difference is small (i.e. less than 1%) within the ranges usually seen in HVAC applications. However it is significant at relative humidities less than 30% and temperatures less than 45F. This degree of error is built into the ASHRAE correlations and is not the result of our code. We are looking into the source of the discrepancy and will update the our functions if a better solution is identified. Note that there is very good agreement among the functions (< 1% difference) in terms of evaluation of enthalpy anywhere on the psych chart.Currently the functions are only written for English units. If there is sufficient demand we will be happy to release a metric version. Send email to psych@kw-energy.com if you would like to see a metric version.

The functions in the library are the following:

enthalpy(T,P,Situation,StateVar) [Btu/lb]dewpoint(T,P,Situation,StateVar) [F]humidity(T,P,Situation,StateVar) [%, 0.0 to 1.0]humidratio(T,P,Situation,StateVar) [lbs H2O/lbs dry air]volume(T,P,Situation,StateVar) [ft^3/lb]wetbulb(T,P,Situation,StateVar) [F]

Each function has the form:

psychfunction(T,P,Situation, StateVar)

where: T: temperature [F] P: pressure [psia] Situation: tells the function which state variable you will supply (see below) StateVar: the third state variable (i.e. WB, DP or RH)

The arguments for the functions depend on what is known. Temperature and pressure are always required. The "Situation" corresponds to the ASHRAE-defined situation depending on what third variable is known: Situation = 1 when you know the wet-bulb temperature [F] Situation = 2 when you know the dew-point temperature [F] Situation = 3 when you know the: relative humidity [% as decimal from 0 to 1]

Shortcut:Excel makes using functions easier for you these days. Just do the following:

(1) Press the Paste Function button on the Standard Toolbar.The Paste Function button is labled fx If you dont see the Standard Toolbar or the button, select View | Toolbars | Standard from the menu.

(2) Choose User Defined in the Function category box. A list of functions will appear on the right. Double click on the one that you want to use. A function wizard window will come up to help you use the formula. Just follow the directions from thereIn Excel, the "Add-Ins" choice on my "Tools" menu is grayed-out. Why can't I select it?The menu choice will not be available if you dont have a wookbook open. Just open up a new blank sheet and the Add-Ins menu selection will be available again.

Why do I get the error message PSYCH.XLA is not a valid add-in?Check to verify that you are using Excel Version 97. The PSYCH.XLA add-in is not compatible with previous versions of Excel (including Excel Version 7.0 for Win95). Earlier versions handle add-ins and modules completely differently.

The Psychrometric Function Library isn't one of the choices of available add-ins. Why not?The psychrometric functions library has to be in the correct directory for Excel to see it and add it to the list. On my computer the correct directory is C:\Program Files\Microsoft Office\Office\Library but yours could be different. The easiest way to find where to put it is to use the Find File feature of Win95. Look on the drive where Excel is installed for files with the xla extension (i.e. search for *.xla). Watch out if you have an older version of Excel (such as version 7.0) still in place on you computer. If you put psych.xla in that directory

Why doesnt the Calculate message go away, even when I press F9? This happens sometimes for no apparent reason and seems to be an Excel bug. Pressing F9 (shortcut for Calculate Now) or choosing Calculate Now from the Tools | Options | Calculation tab sometimes has no effect. Fortunately they give us another option. Choose Calc Sheet on the Tools | Options | Calculation tab or press the shortcut key F9.

How do I add my own data to the Psych Chart?The easy way is to start with one of the plots that is given in the spreadsheet template. Add your data on the Data to Graph tab. If you need to plot more than 10 points you can insert rows on the table and copy the humidity ratio functions (the column on the far right) into the empty cells. As long as you insert your rows in between the rows 1 through 10 on the table, the new data will show up on the graph. You can change the format of the points on the graph any way that you like.

You can also add data from your own table. The psych chart is an X-Y plot with dry bulb temperature (T) on the horizontal axis and humidity ratio (W) on the vertical axis. You need to manipulate your data into a table of T and W pairs to plot them. Bring up the "Psych Chart" sheet in the workbook and choose "Chart | Source Data" from the menu. Click on the tab labled "Series" and push the "Add" button in the lower left corner. Put your cursor in the small window labeled "X Values:". Then you can select the range of temperatures in your data. Repeat the procedure to select humidity ratio data for the "Y Values:". You can also put in a title for your series. When you are done click "OK" and your data will be added to the plot. Sometimes it may be hard to spot at first. For some reason my version of Excel chooses an almost invisible color of green to plot the next series. You can use the "Zoom" feature to spot your series on the plot & change the color.

NOTE: DON'T USE THE "ADD DATA" FUNTION ON THE CHART MENUThis function doesn't work well with the psych chart. Use the method described above instead.The Psychrometric Function Library and PSYCH spreadsheet template were created mostly in the wee hours of the night by Jim Kelsey of KW Energy Engineering.

Refer first to the FAQ section above for technical questions. If you have already tried that and you need more help, or have other technical questions send them to:

psych@kw-energy.com

or call us at:

KW Energy Engineering175 Filbert Street, Suite 205Oakland, CA 94607-2541Tel: 510.834.6420Fax: 510.834.6373You can delete this sheet without adversely effecting the other sheets.COPYRIGHT NOTICE Copyright 2002 kW Engineering. All Rights Reserved.

TERMS OF USEThis spreadsheet and the accompanying psychrometric function library are provided as shareware for a trial use period of 60 days. After the trial period has expired, you will need to obtain a licensed version. See our website at www.kw-engineering.com to obtain a licensed version.

By using this spreadsheet you agree to indemnify kW Engineering from any liability that might arise from its use.

Selling the code for this spreadsheet without prior written consent is expressly forbidden.

Obtain written permission from kW Engineering before redistributing this software over the internet or in any other medium.

Sheet1Sheet TemplateAltitude0ftAtmospheric Pressure14.696psiStandard Atmospheric Data for Altitudes to 60,000 ft(from ASHRAE Fundamentals, 1993, p. 6.1 Table 1)AltitudePressure[ft][psia]1-100015.2362-50014.9663014.696450014.4305100014.1756200013.6647300013.1738400012.6829500012.23010600011.77811700011.34112800010.91413900010.506141000010.10815150008.29616200006.75817300004.37118400002.73119500001.69020600001.051

You can specify the altitude and the pressure will be calculated for you.The pressure is calculated automatically from altitude (you can overwrite it)Note that if you change the altitude, the relative humidity labels may need to be repositioned on the graph. You can see correct labels for the lines by holding the pointer over them.DON'T DELETE THIS SHEET!(you can delete anything except the cell holding the pressure value)You can use this sheet as a starting point for your worksheet.

It is important that you you do not delete the cell named "Pressure" (in grey). This is a named variable that is used throughout the workbook.You can move it if you like and delete any other elements on the page (including this text box). You can also rename this sheet.

There is also a table below that is used to look up the atmospheric pressure based on the altitude. You can delete it if you override the lookup function and enter the pressure yourself.

ExamplesExamplesThis sheet shows how to use the psychrometric functions in calculations.Situation 1. (wet bulb is known)Given:Dry-bulb temperaturet70.0FUser Tip:Wet-bulb temperaturewb55.0FUse the "Paste Function" buttonPressurep14.696psiato create formulas using the psychfunctions. Choose the "User Defined"Find:Relative humidityphi37.2%category and then double click on theDew-point temperaturedp42.7Ffunction that you want to use.Humidity ratioW0.00577lbs/lbsEnthalpyh23.1Btu/lbVolumev13.48cf/lbSituation 2. (dew point is known)Given:Dry-bulb temperaturet65.0FDew-point temperaturedp65.0FPressurep14.696psiaFind:Wet-bulb temperaturewb65.0FRelative humidityphi100.0%Humidity ratioW0.01321lbs/lbsEnthalpyh30.0Btu/lbVolumev13.51cf/lbSituation 3. (relative humidity is known)Given:Dry-bulb temperaturet45.0FRelative humidityphi50.0%Pressurep14.696psiaFind:Wet-bulb temperaturewb37.8FDew-point temperaturedp27.4FHumidity ratioW0.00314lbs/lbsEnthalpyh14.2Btu/lbVolumev12.79cf/lb

&APage &PYou can delete this sheet without adversely effecting other sheets.

Data to GraphUse this page to add a series to plot on the psych chartAltitude0ftAdd your values in the green areas.Atmospheric Pressure14.696psiSituation 1. (wet bulb is known)Given:Dry-bulb TemperatureWet-bulb TemperatureHumidity Ratio175600.0075967731265600.0098887227370550.0057707023470700.01576469945060708090100Situation 2. (dew point is known)Given:Dry-bulb TemperatureDew-point TemperatureHumidity Ratio175500.0076304531260500.007630453130405060708090100Situation 3. (relative humidity is known)Given:Dry-bulb TemperatureRelative HumidityHumidity Ratio17541.5%0.007646731528541.5%0.010655832430405060708090100

The value for the pressure is set on Sheet1.Instructions:Add the points that you want to plot to any of the three tables. Choose which table to use based on the variables that you know. The tables correspond to the three situations listed in the examples. Clear the data in the other tables so that only your data is displayed.

You can insert rows as needed if you need to plot more points.

Note that you need at least 2 points for the plot to appear on the graph. You can list the same point twice if you only want to show one point.The value for the altitude is set on Sheet1.You can delete this sheet without adversely effecting other sheets.

Psych Chart0.00037537930.0007512120.00112749890.00150424080.00188143860.0022590930.00263720490.00301577520.00339480460.00377429410.00215781330.00510506030.00749305490.01022227140.01321332910.01640661410.01975771960.02323391370.02681085320.03047017690.03419781620.00759677310.00763045310.00764673150.00042341930.00084741560.00127198990.00169714340.00212287740.0025491930.00297609140.00340357390.00383164150.0042602956000000000000.00988872270.00763045310.01065583240.00051559860.00103205260.00154936440.0020675360.00258656950.00310646710.00362723090.00414886320.00467136610.00519474180000.00062511780.00125149350.00187913070.00250803340.00313820530.00376965030.00440237230.00503637510.00567166270.00630823890000.00075471240.00151125850.00226964510.00302987890.00379196660.00455591510.00532173110.00608942150.00685899320.00763045310000.00090746240.00181757660.00273035430.00364580720.0045639470.00548478570.0064083350.00733460710.00826361390.00919536760000.00108682520.00217745530.00327191010.00437020990.0054723750.00657842590.0076883830.00880226710.00992009920.01104190020000.00129666930.00259875640.00390629520.00521932010.00653786570.00786196690.00919165880.01052697690.01186795710.01321463540000.00154131050.00309027890.00464696250.0062114190.00778370680.00936388490.01095201270.01254815050.01415235890.01576469940000.00182555040.00366184850.00550898960.00736706990.0092361870.01111643950.01300792710.01491075090.01682501310.01875081710000.00215471720.00432441530.00650925130.0087093840.01092497480.0131561870.01540318640.01766614130.01994522220.0222406020.00253470940.00509016230.00766661450.01026432580.01288356050.01552458720.0181876790.02087311360.02358117330.02631214520.00297204240.00597262410.00900215820.01206106580.01514977610.01826872690.02141836430.02459914360.02781152880.03105599350.00347389870.00698682030.01053942610.01413239240.01776641090.02144218930.02516045140.02892193810.03272740750.03657763570.00404818160.00814940380.01230471610.01651519560.02078194830.02510610990.02948884690.03393135760.03843487320.04300065910.00470357410.00947882950.01432741750.01925104040.02425145350.02933046750.03448995030.03973182940.04505809470.05047080030.00544960260.01099554480.01664040420.02238685090.02823765230.03419567680.04026389940.04644540570.0527433980.05916120020.00629670670.01272220850.01928049790.02597573420.03281225210.03979457110.04692740590.05421567630.06166451910.06927929990.00725631640.01468394270.02228901790.03007797790.03805757350.04623489030.05461736910.06321282910.07202949190.0810760077

RH=10%RH=20%RH=30%RH=40%RH=50%RH=60%RH=70%RH=80%RH=90%RH=100%h=10h=15h=20h=25h=30h=35h=40h=45h=50h=55h=60Situation 1Situation 2Situation 3Dry Bulb Temperature (F)Humidity Ratio (lbs H2O per lbs dry air)Psychrometric ChartRH = 20%RH = 40%RH = 60%RH = 80%h = 20 Btu/lb h = 30 Btu/lb h = 40 Btu/lb h = 50 Btu/lb

Plot DataPsychrometric Chart Plotsp14.696psiaRelative Humidity LinesEnthalpy LinesValues in table are W (lbm/lbair)RH =HDry-bulbHDry-bulb [F]10%20%30%40%50%60%70%80%90%100%[Btu/lb][F]w[Btu/lb]RH320.00040.00080.00110.00150.00190.00230.00260.00300.00340.00381032.00.0021610.0057%