Choosing A Chiller

What is a Chiller?

The industrial chiller is a cooling system that removes heat from one element (water) and transfers it into another (ambient air or water).

Cole-Parmer Polystat Air-Cooled Portable Industrial Chiller; 5 to 35°C, 13.2 L/min; 230 VAC, 60 Hz

A chiller is a compressor based cooling system that is similar to an air conditioner except it cools and controls the temperature of a liquid instead of air. The other main components to a chiller are a temperature controller, a recirculating pump and a reservoir. Operation and setup are simple. Fill the reservoir with fluid to be recirculated, typically water or an ethylene glycol/water mix. Install plumbing between the chiller and the application and provide power to the chiller. The controller regulates the chiller’s functions. The chiller will provide a stable temperature, flow and pressure once it has been programmed by a user for their individual needs. Harmful particles are kept out of the system by an internal strainer.

Chiller Types

Portable chiller

A liquid cooling system on casters that can be relocated from one application to another with relative ease. It can be used to cool one or more heat generating devices.

Air-cooled chiller

These chillers absorb heat from process water and can be transferred to the surrounding air.Air-cooled chillers are generally used in applications where the additional heat they discharge is not a factor. They require less maintenance than water-cooled units and eliminate the need for a cooling tower and condense water pump. They generally consume approximately 10% more power than a water-cooled unit as a wet surface transfers heat better than a dry surface.

Water-cooled chiller

These chillers absorb heat from process water and transfer it to a separate water source such as a cooling tower, river, pond, etc. They are generally used for large capacity applications, where the heat generated by an air-cooled chiller creates a problem. They are also considered when a cooling tower is already in place, or where the customer requires optimum efficiency of power consumption. Water- cooled chillers require condenser water treatment to eliminate mineral buildup. Mineral deposits create poor heat transfer situations, that reduce the efficiency of the unit.

Selection Process

Water

Air

1. Adequate water supply available from tower or well source 1. Adequate water supply not available from tower or well sources.
2. Water supply is of good quality. 2. Water supply is not of good quality.
3. Heat recovery is not practical or unimportant. 3. Heat recovery is practical and important.
4. Plant ambient temperatures consistently exceed 95º F. 4. Plant ambient temperatures will not consistently exceed 95º F.
5. Ambient air is polluted with large dust and dirt particles. 5. Ambient air is not polluted with large dust and dirt particles.

Why Buy a Chiller?

Equipment protection

The most compelling reason for a chiller is the protection it provides to valuable processing equipment—such as spot welders, injection molding equipment and other applications. A chiller commonly represents a small fraction of the cost of the processing equipment, yet it provides solid protection of an investment, 24-hours-a-day, 7-days-a-week for many years to come.

Increase production

The speed and accuracy of production will increase as constant and proper cooling temperature in the equipment are maintained. A chiller will reduce the number of rejected parts while increasing the number of parts produced per hour.

Chiller Designs

One chiller cannot control every heat load. Some chillers are designed to cool to very low temperatures while others are designed for only mid-range applications. Some designs can support very high flow rates of fluid while other may be designed for just a trickle of fluid. The same issues apply with ambient temperatures. Some chillers use refrigerant suited for a high ambient temperature environment while other refrigerants are formulated for cooler conditions.

One must also consider the fluid being cooled. Distilled water or di-ionized water requires different conditions than tap water. DI and distilled water can cause the breakdown of metal they come in contact with. In cases like this the chiller is designed with no brass, copper or mild steel components that would come in contact with the water, instead, plastic or stainless steel are used. This eliminates the corrosive effects of the fluid.

Chiller Applications

Chillers are used in many industrial applications. The most common applications are:

Plastics

In the plastics industry chillers are used for cooling the hot plastic that is injected, blown extruded or stamped. Chillers can also be used to cool down the equipment used in the manufacturing process.

Laser

Chillers are used to cool down the lasers and the power supplies used to power them.

Printing

Chillers remove the heat generated by the printing rollers and also cool down the paper after it comes out of the ink drying ovens.

EDM

Chillers keep machinery at ambient temperature during the cutting process.

Machine tooling

Chillers cool the spindle of the machine as it produces the part and cools the liquid being sprayed on part itself as it is being turned on the spindle.

MRI and PET scans

Chillers cool the high powered electronics inside the machines that are the latest in diagnostic tools.

How To Choose An Industrial Chiller

Choosing the right size recirculating chiller adds to the economies of its use. The optimum size needed is based on the amount of heat your application is generating, plus additional power to maintain temperature under varying loads.

Normally the manufacturer of the equipment being cooled will supply heat removal information, which will include BTU/hr or watts to be removed along with flow rate and desired and inlet and outlet temperatures for the equipment.

If information isn’t available, here’s how to calculate the heat load of your system:

BTU/hr = (T1-T2) x gpm x 60 min/hr x 8.33 lb/gal x Cp

T1 = temperature of coolant leaving the equipment, deg F

T2 = temperature of coolant entering the equipment, deg F

gpm = gallons per minute of coolant flowing through the equipment

Cp = specific heat of coolant; Water = 1.0

Measure temperature with the same thermometer if possible of with two thermometers of known accuracy. Measure gpm using a flowmeter of by collecting the coolant in a known volume for a given period of time.

Additional considerations

:

  1. If ambient temperature of the cooling location is above 68°F, add 1% to the calculated BTU/hr for each 0.9°F above 68°F.
  2. If operating at 50Hz, add 20% to the calculated BTU/hr.
  3. If line voltage is consistently below rated voltage, or if you work at high altitude, add 10% to the calculated wattage.
  4. Future growth cooling needs or variability of heat output of existing unit.

Conversions

:
Watts = BTU/hr / 3.413
Tons = (BTU’s / hr) / 12,000

How To Choose A Laboratory Chiller

Choosing the right size recirculating chiller adds to the economies of its use. The optimum size needed is based on the amount of heat your application is generating, plus additional power to maintain temperature under varying loads. Normally the manufacturer of the device you are cooling will supply heat removal information. If information isn’t available, here’s how to calculate the heat load of your system:

Watts

= [DT° x (K)] / S

Where

:

  • DT= The difference (D) between incoming and outgoing tap water temperature (T) of your instrument. Measure carefully using the same thermometer for both locations. You may measure in Celsius or Fahrenheit.
  • S = The number of seconds to fill a one liter container.
  • K = Conversion constant for density and specific heat of water.

Measured in

:
Celsius: Watts = [DT°C (4,186)] / Seconds
Fahrenheit: Watts = [DT°F (2,326)] / Seconds

Additional Considerations

:

  1. If ambient temperature of the cooling location is above 20°C, add 1% to the calculated wattage for each 0.5°C above 20°C.
  2. If operating at 50Hz, add 20% to the calculated wattage.
  3. If line voltage is consistently below rated voltage, or if you work at high altitude, add 10% to the calculated wattage.
  4. Future growth cooling needs or variability of heat output of existing unit.

Conversions

:
BTU’s / hr = (watts) * 3.413
Tons = (BTU’s / hr) / 12,000

Calculating Process Heat Loads

Below are some basic methods for calculating the heat load of various industrial processes. In order to use the heat load calculations some general definitions need to be addressed. The calculations will reference the following basic definitions and formulas:

One Ton of Refrigeration = 12,000 Btu per Hour

One Refrigeration Ton = 3,025 kg calories per hour

Btu/hr for Water = GPM x 500 x Delta-T

Btu/hr for other fluids = Lbs. Per Hr. x Specific Heat x Specific Gravity X Delta-T

Btu/hr for Solids = Lbs. Per hour x Specific Heat x Delta-T

Btu/hr = kW x 3,413

Btu/hr = HP x 2,544

PSIA = PSIG 14.7

Btu/hr = kW x 1000 / .293

kW = Btu/hr / 1000 x .293

Lbs/Hr = GPM x Density x 8.022

Lbs/Hr = GPM x 501.375 x Specific Gravity

Specific Gravity = Density / 62.4

GPM of Water = Btu/hr / Specific Heat / Specific Gravity / Delta-T / 500

Heat Rejection for Common Industrial Machinery

Air Compressors ………………………1,500 Btu/hr per HP
Air Compressor Aftercooler………1,500 Btu/hr per HP
Vacuum Pump Cooling………………1,500 Btu/hr per HP
Hydraulic Cooling………………………2,544 Btu/hr per HP x .6
Hot Runner………………………………..3,420 Btu/hr pr kW

If component heat loads cannot be learned from customer supplied data, multiply the total input Hp or kW times the appropriate conversion factor. This represents the maximum possible heat load.