Engineering Formulas for Chillers, Towers, and MTCUs

Engineering Formulas

Nominal Design Parameters

Chillers: 2.4GPM/Ton @ 10° F ∆T Flow Rate

- 12,000 BTU/HR/Ton
- 20° F – 60° F Standard Supply Range
- Rating at 50° F Supply Temperature
- 85° F Water Cooled Condenser
- 95° F Air Cooled Condenser

Cooling Tower = 15,000 BTU/HR/Ton

3 GPM per Ton
85° F Leaving Water Temperature
95° F Entering Water Temperature
78° F Wet Bulb

Tower water make-up requirements:
Untreated 2% of flow rate Treated 1.5% of flow rate

Weighted Water Test

Chiller Ton = GPMx∆T
(Delta Temp)

24

Tower Ton =GPMx∆T
(Delta Temp)

30

Chiller Sizing

Injection Molding

Blow Molding

Extrusion

30#/hr H.D. Polyethlene = 1ton

40#/hr Polyolefins= 1 ton

50#/hr H.D. Polyethlene = 1 ton

35#/hr L.D. Polyethlene = 1ton

40#/hr PET= 1 ton

50#/hr L.D. Polyethlene = 1 ton

35#/hr Polypropylene = 1ton

Minimum Flow 04.8 gpm/ton

50#/hr Polypropylene = 1
ton

45#/hr PVC = 1 ton

75#/hr Polystyrene = 1 ton

50#/hr ABS= 1 ton

75#/hr PVC = 1 ton

50#/hr Polystyrene= 1 ton

Blown Film Air Ring
Cooling
105 CFM (50 ° F @ 78°
F WBT)= 1 ton

40#/hr Nylon= 1 ton

35#/hr Acrylic= 1 ton

40#/hr Polyurethane = 1 ton

50#/hr Acetal= 1 ton

40#/hr PPO= 1 ton

40#/hr PET= 1 ton

50#/hr Polycarb= 1 ton

Chiller
Capacity Loss/Gain

Decrease nominal
tonnage by approximately 2% per degree below a 50 ° F leaving water
temperature.

Increase nominal
tonnage approximately 2% per degree above 50 ° F leaving water
temperature up to 55 ° F

Other
Equipment

Air Compressor w/no after cooler

=.1 ton/Hp

Air Compressor w/after cooler

=.2 Ton/Hp

Vacuum Pump

=.1 ton/Hp

Hydraulic Cooling

=.1 ton/Hp

Barrel Cooling

=.1 ton/in screw Dia.

Hot Runner Mold

= 1 ton/10.5KW

Water Pump in Circuit

=.2 Ton/Hr

Feed Throat

400Ton Machine or above 1 Ton
Below 400 Ton – 1/2 Ton

Extrusion Equipment

Gear Box Cooling

=1 Ton/100Hp

Feed Throat 3″ Screw or Less

=1 Ton

Above 3″ Screw

=2 Tons

Barrel or Screw Cooling

=1 Ton/Inch of Screw Diameter

Pipe
Sizing Guide
(Based on 5′ – 7′ feet/second
velocity)

1/8” = .75 GPM	3/4″ = 10 GPM	2″ = 70 GPM	6″ = 600 GPM
¼” = 1.5 GPM	1″ = 15 GPM	2 1/2″ = 100 GPM	8″ = 1,000 GPM
3/8” = 3 GPM	1 1/4″ = 30 GPM	3″ = 150 GPM	10″ = 3000 GPM
1/2″ = 6 GPM	1 1/2″ = 40 GPM	4″= 275 GPM	12″ = 5000 GPM

Metric
Conversion Chart

To
Convert

To Convert

Unit Volume

Power

US GPM

Liters/Min

3.785

FT/Lb/SEC

Watts

1.356

US GPM

Cum/Hr

.2271

KW

BTUH

342

CFM

Liters/Min

28.317

Boiler HP

BTUH

33475

CFM

Cum/hr

1.6992

HP

BTUH

2545

Unit Weight

HP

KW

.7457

Lb/Ft

Kg/m

1.4881

Lbs/Sq in

gr/sq cm

70.31

Heat

Lbs/Sq in

kPA

6.894

BTU

Kg-cal

.252

Lbs/Sq in

Kg/Sq Cm

.07031

BTU/LB

Kg-cal

.5556

Lbs/Sq in

gr/cu cm

27.68

BTU/SQ FT

gr-cal/sq cm

.2713

Length

BTU/CU FT

Kg-cal/Cum

8.899

Inches

cm

2.540

Weight

Feet

meters

.3048

Grains

grams

.0648

Yards

meters

.9144

Ounces*

grams

28.350

Miles

km

1.609

LBS

kg

.4536

Volume

US tons

kg

907.2

Cu. Inches

cu cm

16.387

US Tons

Tonnes

.9072

Cu. Inches

liters

.01639

Long Tons

kg

1016

Cu Feet

cu meter

.02832

Area

Cu Feet

liters

28.317

SQ Inches

sq cm

6.452

Cu Years

cu meters

.7646

SQ Years

sq meters

.8361

Fl Ounces

cu cm

29.57

SQ Miles

sq km

2.590

US Gallon

cu meters

.003785

US Gallon

liters

3.785

*Auoirdupois pounds and ounces

*Temperature*
°F	°C	°F	°C	°F	°C	°F	°C
0	-17.8	35	1.7	15	-9.4	50	10.0
5	-15	40	4.4	20	-6.7	55	12.8
10	-12.2	45	7.2	30	1.1	60	15.6
°F to °C = (°F – 32) x .55 =°C				°C to °F = (°C x 1.8) + 32 =°F

Flow Rate Vs. Temp Differences Per Ton	% Ethylene Glycol by Volume vs Freeze Protection
1.2 GPM = 20 °F T	10% 25°F
2.4 GPM = 10 °F T	20% 15°F
4.8 GPM = 5 °F T	30% 0°F
9.6 GPM = 2.5 °F T	40% -15°F
	50% -40°F
Abbreviations, Equivalents & Formulas
T = Delta Temperature = Temperature Differential
PSI = Pounds per square inch	1 Cooling Tower Ton= 15,000BTU/HR
GPM = Gallons per Minute	1 Refrigerant Ton = 12,000 BTU/HR
EWT = Entering Water Temperature	1 Gallon = 8.33 lbs (water)
LWT = Leaving Water Temperature	1 Cubic Foot = 7.48 gallons
BTU = British Thermal Unit	1 Mil = .001″
BTU/HR = GMP x 500 x . T (water)	1 Bar = 14.7 PSI
1 HP = 2544 BTU/HR	1 KW = 3413 BTU/HR
Ft. H.D. = PSI x 2.31	1 KW = 1.34 HP
Q=4.5 x CFM x H = BTUH (Air Cooling)	PSI= Ft of head/2.31
Pump HP= . GPM x P (Ft.H.D) .3960 x (0.65 to 0.75) (Pump Eff)	KW = Amps x Volts x 0.85 x 1.731,000

Head
in Feet to PSI Conversions calculator

Filtration
Chart

Mesh

Micron

Inches

Mesh

Micron

Inches

4

5205

0.2030

80

177

0.0070

8

2487

0.0970

100

149

0.0059

10

1923

0.0750

120

125

0.0049

14

1307

0.0510

140

105

0.0041

18

1000

0.0394

170

88

0.0035

20

840

0.0331

200

74

0.0029

25

710

0.0280

230

62

0.0024

30

590

0.0232

270

53

0.0021

35

500

0.0197

325

44

0.0017

40

420

0.0165

400

37

0.0015

45

350

0.0138

550

25

0.0009

50

297

0.0117

800

15

0.0006

60

250

0.0098

1250

10

0.0004

70

210

0.0083

5

0.0002