制冷技术英文考试试题

Chapter.3RefrigerantsSecondaryRefrigerantandMoistureair

一．Choice

1.Undesirablerefrigerantcharacteristicsare:

a.nonflammableandnontoxic

b.highlatentheatandlowboilingpoint

c.highcriticaltemperatureandlowfreezingpoint

d.lowcriticaltemperatureandhighfreezingpoint

(RefrigerationLicenseExaminations,USA)

2.Adesiredchemicalrefrigerantcharacteristicis:

a.itmixesreadilywithoil

b.stability

c.itcaneasilychangefromaliquidtovaporandback

d.alloftheabove

3.Whatrefrigerantbreaksdownandformsphosgeneinthepresenceofacarbonflame?

a.R-718c.R-764

b.R-717d.R-11

4.Anhydrousammoniais:

a.amixtureofammoniaandwater

b.29%aquaammonia

c.ammoniawithoutanywater

d.noneoftheabove

5.Refrigerantissubcooledto:

a.increasetherefrigerationeffect

b.increasedensity

c.increasemiscibilityinoil

d.noneoftheabove

6.AnywaterintherefrigerantofaFreonsystemwouldcause:

a.acloggedoiltrap

b.acloggedscaletrap

c.afrozendischargevalve

d.afrozenexpansionvalve

7.Ofthefollowingrefrigerants,whichistheleastflammableandtheleasttoxic?

a.methylchloride.c.propane

b.ammoniad.R134a

8.Calciumchloridefreezesat:

a.-41ºFc.35ºF

b.-32ºFd.20ºF

9.Thetermtoxicitymeans:

a.acidityorcorrosivenessc.diffusiveness

b.poisonousnessd.internalfriction.

10.Ofthefollowingtemperatures,whichisthelowestrecommendedforusewithcalciumchloridebrine?

a.0℃c.-41.8℃

b.-35.7℃d.-61.2℃

11.WhichchemicalderivedfromCFCdepletestheozonelayerintheatmosphere?

a.carbondioxidec.carbonmonoxide

b.chlorinemonoxided.calciumchloride

12.Ofthefollowingthermalpropertiesofarefrigerant,theundesirableonesare:

a.highviscosityandlowpourpoint

b.highlatentheatofevaporation

c.lowcriticalandhighfreezingtemperature

d.highviscosityandhighfilmheatconductivity

13.R-718is:

a.methylchloridec.carbondioxide

b.dichlorodifluoromethaned.water

14.Containersshouldnotbecompletelyfilledwithliquidrefrigerantbecause:

a.theywouldbetooheavytocarry

b.ifthetemperaturegoesup,hydrostaticpressurescouldrupturethecontainer

c.therewouldn’tbeanyvaporpresent

d.moistureintheliquidcancausephosgene

15.Ifthespecificgravityofcalciumbrineincreasedfrom1.29tol.30,thefreezingpointwould:

a.notbeaffectedc.drop

b.fluctuateupanddownd.rise

16.Sodiumchloridecannotbeusedforabrinesolutionbelow:

a.-15ºFc.30ºF

b.15ºFd.noneoftheabove

17.Abrinesolutiontobeusedat-25ºFmaynotcontain:

a.calciumchloridec.ethyleneglycol

b.sodiumchlorided.alcohol

18.Theamountofchromaterequiredtomakel,000cubicfeetofcalciumbrineis:

a.50lbs.c.125lbs

b.75lbs.d.200lbs

19.Thefreezingpointofbrineshouldbe:

a.32ºF

b.0ºF

c.10to15ºFbelowthelowestrefrigerantsaturationtemperature

d.-59ºF

20.Theevaporatorabsorbsheatfromairorbrinebecauseliquidrefrigerantenteringit:

a.hasalowertemperaturethantheairorbrine

b.hasahighertemperaturethantheairorbrine

c.boilstoalow-pressuregas

d.boilstoahigh-pressuregas

21.WhichchemicalderivedfromCFCdepletestheozonelayerintheatmosphere?

a.carbondioxidec.R12

b.R407Cd.R134a

22.Thetemperatureatwhichmoistureintheairstartstocondenseinthesurfaceoftubeinaircoolerisknownas:

a.relativehumidityc.eutecticpoint.

b.dewpointd.wet-bulbtemperature

二、Questionandanswer

WhatareCFC,HCFC,HFC,ODPandGWP,whyareCFCsphase-out?Whatis

PhaseOutDate

aboutCFCsandHCFCs,respectively?

2．Whatisheatpump?whatisthedifferencebetweenrefrigerationmachineandheatpump?

三．Calculation

1.Calculatethesensibleheat(enthalpyofdryair)of5kgofairhavingaDryBulbtemperatureof15℃andaDewPointtemperatureof3℃.

2.Determinethelatentheat(enthalpyofthewatervapor)of10kgofairhavingaDryBulbtemperatureof18℃andaDewPointtemperatureof8℃.

3.ReadingsfromaslingpsychrometerindicatethattheairinaroomhasaDryBulbtemperatureof39℃andaWetBulbtemperatureof26℃.Fromthepsychrometricchart,determinethehumidityratio,DewPointtemperature，approximatespecificvolume,specificenthalpyatsaturation,enthalpydeviation,actualspecificenthalpy,andapproximaterelativehumidity.

4.Onethousandkilograms0fairperhourhaveDryBulbandDewPointtemperaturesof28℃and16℃,respectively,andarepassedacrossacoolingcoilandcooledtoafinalDryBulbtemperatureof8℃.Assumingthattheairleavingthecoilissaturated.Determine:(a)themassofthewatervaporcondensedfromtheairinkilogramsperhourand(b)therateoflatentheatremovalinkilowatts.(c)Calculatethetotalheatinkilowattsremovedfromtheair.

5.Twokilo