Trane trg-trc001-en User Manual

Air ConditioningClinicPsychrometryOne of the Fundamental SeriesTRG-TRC001-EN

TRG-TRC001-EN 3period oneThe Psychrometric ChartnotesDry-bulb temperatures are read from an ordinary thermometer that has a dry bulb.Wet-bulb temperat

4 TRG-TRC001-ENnotesperiod oneThe Psychrometric ChartThe third property, dew-point temperature, is the temperature at which moisture leaves the air an

TRG-TRC001-EN 5period oneThe Psychrometric ChartnotesThe fourth property, relative humidity, is a comparison of the amount of moisture that a given am

6 TRG-TRC001-ENnotesperiod oneThe Psychrometric ChartFinally, humidity ratio describes the actual weight of water in an air – water vapor mixture. In

TRG-TRC001-EN 7period oneThe Psychrometric ChartnotesFor example, let's assume that the summer design conditions are 95°F dry bulb and 78°F wet b

8 TRG-TRC001-ENnotesperiod oneThe Psychrometric ChartNotice that the point of intersection falls between two relative humidity curves: 40% and 50%. B

TRG-TRC001-EN 9period oneThe Psychrometric ChartnotesThese saturation points can be plotted on a chart with dry-bulb temperature along the horizontal

10 TRG-TRC001-ENnotesperiod oneThe Psychrometric ChartAnother fact about saturated air should be discussed before we proceed.Assume a volume of moist

TRG-TRC001-EN 11period oneThe Psychrometric ChartnotesAdditionally, the dew-point temperature does not change as the dry-bulb temperature changes, pro

12 TRG-TRC001-ENnotesperiod oneThe Psychrometric ChartAdditional curves can be added to the chart to represent relative humidity conditions that are l

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TRG-TRC001-EN 13period oneThe Psychrometric ChartnotesTo complete this basic chart, the wet-bulb temperature lines must be added.Once again, at a satu

14 TRG-TRC001-ENnotesperiod oneThe Psychrometric ChartThe psychrometric chart now defines these five properties of air: dry-bulb temperature (vertical

TRG-TRC001-EN 15period oneThe Psychrometric ChartnotesEffect of Sensible Heat and Moisture ChangesWhen either the sensible heat content or the moistur

16 TRG-TRC001-ENnotesperiod oneThe Psychrometric ChartOn the other hand, if moisture is added to air without changing the dry-bulb temperature, the ai

TRG-TRC001-EN 17period oneThe Psychrometric ChartnotesPut all of these changes together on one chart and they show the direction the air condition wil

18 TRG-TRC001-ENnotesBefore an air conditioning problem can be analyzed on the psychrometric chart, the conditions of the air to be cooled or heated m

TRG-TRC001-EN 19period twoAir MixturesnotesIf outdoor air B is mixed with recirculated air A, the conditions of the resulting mixture are found somewh

20 TRG-TRC001-ENnotesperiod twoAir MixturesThe outdoor air quantity in this example constitutes 25% of the mixture, while the recirculated air makes u

TRG-TRC001-EN 21period twoAir MixturesnotesReturning to the psychrometric chart, point C, at which the 83.75°F dry-bulb temperature falls on the line

22 TRG-TRC001-ENnotesperiod threeSensible Heat RatioThis period is devoted to understanding the term sensible heat ratio and how it is represented on

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TRG-TRC001-EN 23period threeSensible Heat RationotesConversely, if only latent heat is removed, the line moves vertically downward along a constant dr

24 TRG-TRC001-ENnotesperiod threeSensible Heat RatioImagine conditioned supply air as a sponge. As it enters a room, it absorbs heat and moisture. The

TRG-TRC001-EN 25period threeSensible Heat RationotesWhen the required amount of sensible and latent heat are not properly removed from the room, the d

26 TRG-TRC001-ENnotesperiod threeSensible Heat RatioThis relationship between the conditions and quantity of the supply air can be described using the

TRG-TRC001-EN 27period threeSensible Heat RationotesThe sensible heat ratio, abbreviated as SHR, refers to the comparison of sensible heat gain to tot

28 TRG-TRC001-ENnotesperiod threeSensible Heat RatioAssume that room design conditions (A) are 78°F DB and 65°F WB, and that the sensible heat ratio i

TRG-TRC001-EN 29period threeSensible Heat RationotesSensible-heat-ratio lines for other conditions are drawn in the following manner. Assume that room

30 TRG-TRC001-ENnotesperiod fourAir QuantityNext, we will determine the flow rate of supply air necessary to maintain a given set of design room condi

TRG-TRC001-EN 31period fourAir QuantitynotesTo demonstrate how the required supply airflow is determined, assume that a room’s sensible heat gain is 8

32 TRG-TRC001-ENnotesperiod fourAir QuantityPlot the outdoor air B (95°F DB, 78°F WB) and indoor air A (78°F DB, 65°F WB) conditions on the psychromet

PsychrometryOne of the Fundamental SeriesA publication ofThe Trane Company—Worldwide Applied Systems Group

TRG-TRC001-EN 33period fourAir QuantitynotesThe third step is to determine the required supply air conditions. This is where the coil curves are used.

34 TRG-TRC001-ENnotesperiod fourAir QuantityWith the supply air conditions known, the next step is to calculate the specific quantity of air (cfm or c

TRG-TRC001-EN 35period fourAir QuantitynotesFor this example, the supply airflow is calculated as follows:The cooling coil must cool and dehumidify 3,

36 TRG-TRC001-ENnotesperiod fourAir QuantitySome designers prefer to set the supply air temperature at 55°F or use a 20°F temperature differential (Ro

TRG-TRC001-EN 37notesperiod fiveTons of RefrigerationThe psychrometric chart can also be used to determine the total load on the refrigeration equipme

38 TRG-TRC001-ENnotesperiod fiveTons of RefrigerationUsing the previous example for calculating supply airflow, the first step is to determine the ent

TRG-TRC001-EN 39period fiveTons of RefrigerationnotesRealize that 4.5 is not a constant! It is the product of density of air and the conversion factor

40 TRG-TRC001-ENnotesperiod fiveTons of RefrigerationThe psychrometric chart can also be used to determine the sensible and latent components of the c

TRG-TRC001-EN 41period fiveTons of RefrigerationnotesBy determining the enthalpy values for these three points, the same equation can be used to calcu

42 TRG-TRC001-ENnotesperiod sixPsychrometric AnalysesNow we will look at a few ways that the psychrometric chart can help us analyze air conditioning

Preface© 1999 American Standard Inc. All rights reservedTRG-TRC001-ENiiThe Trane Company believes that it is incumbent on manufacturers to serve the i

TRG-TRC001-EN 43period sixPsychrometric AnalysesnotesFor example, assume that at full load the room is subject to an 80,000 Btu/hr sensible heat gain

44 TRG-TRC001-ENnotesperiod sixPsychrometric AnalysesIn response to the reduction in room sensible heat gain, the coil capacity is throttled, raising

TRG-TRC001-EN 45period sixPsychrometric AnalysesnotesThis is the manner in which a constant-volume, variable-temperature system with a modulating coil

46 TRG-TRC001-ENnotesperiod sixPsychrometric AnalysesUsing the part-load conditions from the previous example, the room’s sensible heat gain is reduce

TRG-TRC001-EN 47period sixPsychrometric AnalysesnotesThis supply air mixes with room air along the part-load 0.70 SHR line from E to A, arriving at th

48 TRG-TRC001-ENnotesperiod sixPsychrometric Analysesvarying the supply air temperature as the two airstreams mix downstream of the air handler.The fa

TRG-TRC001-EN 49period sixPsychrometric AnalysesnotesThis supply air E mixes with room air along the part-load 0.70 SHR line, arriving at the resultin

50 TRG-TRC001-ENnotesperiod sixPsychrometric AnalysesAt part load, when the SHR of the room is reduced from 0.80 to 0.70, the VAV system responds by r

TRG-TRC001-EN 51period sixPsychrometric AnalysesnotesThe psychrometric chart is a visual tool that helps designers find solutions to many common HVAC

52 TRG-TRC001-ENnotesLet’s review some of the main concepts from this clinic on psychrometry.The lines of the psychrometric chart represent five physi

TRG-TRC001-EN iiiContentsperiod one The Psychrometric Chart ... 1Properties of Air ...

TRG-TRC001-EN 53period sevenReviewnotesIn Period Two, a method was discussed to determine the resulting properties of an air mixture. By plotting the

54 TRG-TRC001-ENnotesperiod sevenReviewAfter determining the entering air conditions for the coil and the slope of the SHR line, the coil curves were

TRG-TRC001-EN 55period sevenReviewnotesThe resulting psychrometric chart plot represents the changes that a volume of air undergoes as it travels thro

56 TRG-TRC001-ENnotesperiod sevenReviewFor more information, refer to the following references: Trane Air Conditioning Manual ASHRAE Handbook—Fundam

TRG-TRC001-EN 57Questions for Period 11 Given air conditions of 80°F DB and 60% RH, find the humidity ratio and dew-point temperature.2 Given air cond

58 TRG-TRC001-ENQuizQuestions for Period 49 Given a room with a 42,000 Btu/hr sensible heat gain and a 56,000 Btu/hr total heat gain (excluding ventil

TRG-TRC001-EN 591 93 grains/lb, 64.8°F DP2 49.5% RH, 70.5°F WB3 85°F DB, 110 grains/lb4 41% RH, 64°F WB5 56°F DP, 32% RH6a95°F × 0.20 = 19°F80°F × 0.8

60 TRG-TRC001-ENAnswers8aThe SHR line crosses the saturation curve at 56°F WB (See Figure 92.)b 60°F DB, 58°F WB (See Figure 92.)9abSee Figure 93.

TRG-TRC001-EN 61Answers1058.3°F WB (See Figure 94.)11))6+56+5Figure 93SHR80,000 Btu/hr80,000 Btu/hr 20,000 Btu/hr+

62 TRG-TRC001-ENAnswers12 See Figure 95.13 a See Figure 96.bcdRefrigeration Load 4.5 7,000 cfm× 33.2 24.2–()× 283,500 Btu/hr==283,500 Btu/hr12,000 Btu

iv TRG-TRC001-EN

TRG-TRC001-EN 63Answersefg))6+56+5))))Figure 96Airflow (cfm)156,000 Btu/hr1.085 78°F57°F–()×

64 TRG-TRC001-ENASHRAE American Society of Heating, Refrigerating and Air-Conditioning Engineerscoil curves These represent the changes in dry-bulb an

TRG-TRC001-EN 65Glossarysaturation curve This represents the moisture content that constitutes complete saturation of air at the various dry-bulb temp

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TRG-TRC001-EN 1notesperiod oneThe Psychrometric ChartPsychrometry is the science dealing with the physical laws of air – water mixtures.When designing

2 TRG-TRC001-ENnotesperiod oneThe Psychrometric ChartProperties of AirAt first glance, the psychrometric chart appears to be an imposing network of li