Premier Industries, Inc.
   INDUSTRIAL EVAPORATIVE PRECOOLER

INTRODUCTION: 
   
The performance of most, if not all air cooled heat generating equipment decreases inversely with temperature rise. 
A common example of this is the air cooled condenser coils of air conditioners.  This is illustrated in the following example of a Typical Trane Chiller Model RTAC250STD, commonly referred to as a 240 Ton Chiller.

Water

Temp

Out

AMBIENT TEMPERATURE (F)

85F

95F

105F

115F

 

TONS

KW IN

EER

TONS

KW IN

EER

TONS

KW IN

EER

TONS

KW IN

EER

42F

244.8

247.9

10.9

229

268.5

9.5

212.7

292

8.2

195.7

318.2

6.9

 

The graph below illustrates this effect.

 

 

 

 

 

 

 

 


 

    Following is an illustration of a typical approach to determine the need for precooling. Some equipment cannot meet cooling needs during extremely hot temperatures. Pre-cooling the air is often the simple solution to increase output and reduce operating costs of the equipment and extend the useful lifespan. 

           

This application involves (3) 250 TON Trane Air Cooled Chillers Model RTAC 250STD installed in a hot dry region, on a ground level concrete slab as shown above.

Equipment Footprint

 

This is a plot of the Chillers footprint. It is to be noted that space is a serious consideration. Piping location is another problem. Precooling system selection is limited.
 

                           Powered Evaporative Cooler Layout                                                 
 

A good method of pre-cooling the air in this application is with powered evaporative coolers to deliver air to the condenser fans along the floor level through metal ducts as indicated in this drawing.  It is not practical to attach precooler modules directly to the Condenser Coil sections.

Pre-cooling Performance Comparison

PERFORMANCE WITHOUT   PRECOOLING

         PERFORMANCE WITH        PRECOOLING

 

PERFORMANCE IMPROVEMENT WITH PRECOOL

TEMP (F)

TONS

KWH

EER

AMB TEMP

TONS

KWH

EER

TONS

KWH

85

244.8

247.9

10.9

85

249.8

242.9

11.2

5

-4.96

95

229

268.5

9.5

95

249.8

242.9

11.2

20.8

-25.6

105

212.7

292

8.2

105

249.8

242.9

11.2

37.1

-49.1

115

195.7

318.2

6.9

115

249.8

242.9

11.2

54.1

 

-75.3

NOTE:  PRECOOLER DISCHARGE TEMP IS LESS THAN 80F @ 115F AMB TEMP.BASED ON LAS VEGAS, NV., CLIMATE DATA.

 

Estimated Energy Cost Savings

    ESTIMATED KW COST SAVINGS WITH PRECOOLING

AMB TEMP

KWH SAVINGS

AVAIL HOURS

ANNUAL SAVINGS

85 TO 95

$.55

737

$947.33

95 TO 105

$2.82

721

$2030.34

105 TO 115

$5.40

166

$896.57

115 +

$8.28

100

$828.30

 

TOTAL I CHILLER

2724

$4702.53

 

TOTAL 3 CHILLERS

3 UNITS

$14,107.58

NOTE 1.  KWH COST IS BASED ON $.11/KWH.  AVAILABLE HOURS FOR EVAPORATIVE COOLING IS BASED ON WEATHER DATA HANDBOOK USING A 3 YEAR RUNNING AVERAGE MEASURED AT NELLIS AFB AT 50' ABOVE GROUND.  IT IS TO BE NOTED THAT THE ACTUAL GROUND TEMPERATURE IN DIRECT SUNLIGHT IS MUCH HIGHER.
NOTE 2:  COSTS OF ELECTRIC, WATER AND MAINTENANCE OF COOLERS OFFSET BY UNSTATED SAVINGS OF LESS CHILLER OPERATION AND EXTENDED USEFUL LIFESPAN.

         

                                        

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