Welcome to PolyScience’s Cool School. Here you will learn how to choose the product that best suits all of your cooling needs. Please take some time to read through the information. We hope it is informative and helps you to make the right choice for your company.

 

Instant Fact Finder

What is a Chiller
Chiller Types
Why Buy A Chiller
Chiller Designs
Chiller Applications
What is the Refrigeration Process
The PolyScience Refrigeration System
Differences Between a Chiller and a Circulator
How to Choose a Chiller
How to Choose an Industrial Chiller
Sizing a Chiller for Plastics Processing
How to Choose a Laboratory Chiller
Calculating Process Heat Loads
Heat Rejection for Common Industry Machinery
Congratulations Graduate

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).

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 is 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 your 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 your investment, 24-hours-a-day, 7-days-a-week for years and years to come.

Increase Production
The speed and accuracy of production will increase as you maintain a constant and proper cooling temperature in the equipment. 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.

The customer 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.

What is the Refrigeration Process?

Refrigeration is the removal and relocation of heat. So if something is to be refrigerated, it is to have heat removed from it. In order to refrigerate something, you must find a way to expose it to something that is colder than itself and nature will take over from there.

In order to understand the concept of refrigeration you must understand the concept of heat. Long ago a definitive method was developed to quantify heat. Heat is quantified by a measurement called a British Thermal Unit. When 1 LB of water is heated 1 degree Fahrenheit the amount of heat required for the process is called a British Thermal Unit. This is the standard measurement for heat in the refrigeration industry today. The BTU concept applies until a liquid reaches its boiling point. The boiling point of water is 212º. Something very important happens when water is at its boiling point. Once it reaches that point you could keep adding BTU’s, but the water would not get any hotter. It would change its state into a gas and it would take 970 BTU’s to vaporize that pound of water. This is called the Latent Heat of Evaporization and in the case of water it is 970 BTU’s per pound.

Why doesn’t the water boil when it is at room temperature? Surprisingly, it isn’t because the water isn’t hot enough at room temperature. The only thing that keeps the water from boiling is the pressure of the air molecules pressing down on the surface of the water. When you heat that surface to 212º and then continue to add heat, what you are doing is supplying sufficient energy to the water molecules to overcome the pressure of the air and allow them to escape from the liquid state. The atmospheric pressure of the environment, determines the amount of heat needed to vaporize the water. In outer space, where there is no air pressure, the water would vaporize into a gas in a flash. The lower the air pressure the lower the boiling point. If the water were placed under a bell jar and all the pressure removed, the water would boil at room temperature.

We can look at this from another point of view. When liquid evaporates it absorbs heat from the surrounding area. So finding a liquid that would evaporate at a lower temperature than water was one of the first steps needed for the development of mechanical refrigeration. Chemical engineers experimented for many years before finding the perfect chemicals for the job. A family of hydroflourocarbon refrigerants which have extremely low boiling points (below 0º F) were the answer.

There are four main components to a mechanical refrigeration system:

  1. Compressor – a pumping device used to increase pressure of a gas
  2. Condenser – a device used to convert a high pressure gas into a lower pressure liquid by removing heat via forced air, water coil, etc.
  3. Metering device – a device used to control and meter refrigerant flow to a heat exchanger.
  4. Evaporator – a heat exchanger which cools the water, water/glycol or air by transferring the heat to the refrigerant which is turned into a gas
The compressor is a vapor compression pump which uses pistons or some other method to compress the refrigerant gas and send it on it's way to the condenser. The condenser is a heat exchanger which removes heat from the hot compressed gas and allows it to condense into a liquid. The liquid refrigerant is then routed to the metering device. This device restricts the flow by forcing the refrigerant to go through a small hole which causes a pressure drop. And what happens to a liquid when the pressure drops? It lowers the boiling point and makes it easier to evaporate. And what happens when a liquid evaporates? The liquid will absorb heat from the surrounding area? This is how refrigeration works. The component where the evaporation takes place is called the evaporator. The refrigerant is then routed back to the compressor to complete the cycle. The refrigerant is used over and over again absorbing heat from one area and relocating it to another. Remember the definition of refrigeration? (the removal and relocation of heat).

 

The PolyScience Refrigeration System


Differences Between a Chiller and a Circulator

Select a circulator when temperature stability is what’s desired, select a chiller when heat removal is what’s desired.

Circulator


Chiller

 

Chiller or Circulator – How to Choose

What is the Application?
Knowledge of the application may allow you to skip several steps

What is the Temperature Range?
< 30°C? Think refrigeration >30°C? Think Heating only

What Temperature Stability is Required?
±0.01°C? Think circulator ±0.5°C? Think chiller

Closed Loop or Open Bath Application?
If closed loop, think anything but immersion circulator

How Much Cooling Power is Required?
Modest (100 – 700 watts) Strong (750 & up) Think circulator Think chiller

What are the Pumping Requirements:

Circulators Chillers
Simplex – closed loop only Magnetic Drive Centrifugal – fixed flow/ fixed pressure
Duplex – closed or open loop systems Positive Displacement – fixed flow/adjustable pressure
  Turbine – adjustable flow or pressure


Other Requirements?
Remote probe
RS232 port
Expanded programming capabilities
Special fluids – watch compatibility and safety

Overall
Select circulators for temperature control and stability
Select chillers to provide best cooling power / heat removal

 

A Simple Quiz to see What You Have Learned

1. If you need a temperature range below 30°C, what applies?¨
Refrigeration
Heating only

Answer 1: Refrigeration

2. A Duplex Pump is required for?¨
A Closed system¨
An Open system

Answer 2: Open System

3. You want to put several flasks in a tank and control them at 56°C. The combined flasks will occupy 20cm x 20cm. A digital display of temperature is needed. Stability needed is ±0.5°C. What do you need?

Answer 3: Immersion Circulator Model 7306 with a large Stainless Steel Open Bath or a large Acrylic Open Bath. Note the Immersion Circulator occupies 16.5cm x 12cm of the tank.

4. Your Laser company wants a model able to operate at 20°C, and needs to cool down a laser that requires a cooling capacity of up to 2500 watts of heat. You also requires a pressure rate of 25 psi.

Do you need?
A Circulator
A Chiller

Consider:
Desired temperature is below 30°C
Desired cooling capacity is more than 750 watts
Desired pressure rate is more than 10 psi

Answer 4: Chiller

5. This is a Polymer Testing Application. You need a powerful heater and a
reservoir capacity of 28 liters. The process will operate at a temperature range of
130°C to 150°C. The process must circulate out to an open bath.

What model does he need?
Heating Circulator Model 812
Heating Circulator Model 8102
Heating Circulator Model 8202

Consider:
Desired reservoir capacity is 28 liters
Desired temperature range is above 30°C
Desired circulation to an external bath

Answer 5: Model 8102

6. You need to cool an Electrophoresis apparatus, maintaining 20°C with a
stability of ±0.3°C. The cooling requirement is 50W at 20°C. You would also like
to read the temperature at a glance.

What model do you need?
Refrigerated Circulator
Model 912 Refrigerated Circulator
Model 9106 Refrigerated Circulator
 Model 9112 Refrigerated Circulator

Consider:
Desired temperature is 20°C
Desired stability of ±0.3°C
Desired cooling capacity is 50 watts
Desired display

Answer 6: Model 9106


7. You need to cool an ICP, maintaining 20°C and a stability of ±0.5°C. The cooling requirement is 2200 watts at 20°C. The application needs 7.5 lpm @
24 psi. You would also like to read the temperature at a glance.

What model do you need?
Recirculating Chiller Model 6106
Recirculating Chiller Model 6706P
Recirculating Chiller Model 6206

Consider
Desired temperature is 20°C
Desired stability is ±0.5°C
Desired Cooling of 2200 watts @ 20°C
Desired flow/pressure of 7.5 lpm @ 24 psi

Answer 7: Model 6706P

8. You want to control the temperature of Methanol at -35°C and put a beaker of sample into the bath every hour. The stability needed is ±0.1°C and there are no other special needs.

What do you need?
Refrigerated Circulator Model 9506
Refrigerated Circulator Model 9706
Refrigerated Circulator Model 9702

Consider:
Desired temperature is -35°C
Needed cooling is minimal
** Methanol is flammable and not a suitable fluid. The recommended low temperature/low viscosity fluid is Dynalene supplied by PolyScience.

Answer 8: Model 9706

 

How to Choose a Chiller

Chillers have many applications. To be sure that you have chosen the right chiller for your application we offer two selection methods, one for an industrial user and one for a laboratory user. If you have any questions that have not been answered, we are always available to guide you in your selection. Perhaps you have special needs that have to be addressed. Our Customer Service, Sales and Engineering teams are at your disposal to offer additional information or handle any customization issues you might have.

 

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 you are cooling 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. 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. 2. If operating at 50Hz, add 20% to the calculated BTU/hr.
  3. 3. If line voltage is consistently below rated voltage, or if you work at high altitude, add 10% to the calculated wattage.
  4. 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

 

Sizing A Chiller For Plastics Processing

Calculating Cooling Required

[(LB PER HOUR BEING PROCESSED) /MATERIAL FACTOR]*3519 = WATTS OF COOLING REQUIRED

EXAMPLE: Look at the list below and find the smallest material factor for the materials you are processing. If you are injection molding Nylon and ABS then choose the material factor for Nylon which is 40. If you are injection molding Nylon at a rate of 220 lb/hr, then:

(220/40)*3519 = 19355 Watts

Conversions

BTU/hr = Watts * 3.41
Tons = BTU/hr / 12000

Look at the cooling capacity chart for DuraChill and select the DCA750 or DCW750.

MATERIAL FACTORS FOR VARIOUS PROCESSES

INJECTION MOLDING

30 lbs/hour HDPE
35 lbs/hour LDPE
35 lbs/hour Acrylic
35 lbs/hour Polyproplene
40 lbs/hour Nylon
40 lbs/hour Delrin
40 lbs/hour Urethane
45 lbs/hour PET
50 lbs/hour Polystyrene
50 lbs/hour ABS
50 lbs/hour Polycarbonate
50 lbs/hour Acetal
70 lbs/hour PVC

BLOW MOLDING

40 lbs/hour HDPE
40 lbs/hour PET
40 lbs/hour PVC

SHEET CALENDERING EXTRUSION

35 lbs/hour PE
60 lbs/hour ABS
60 lbs/hour PS

PROFILE EXTRUSION

50 lbs/hour HDPE
50 lbs/hour LDPE
50 lbs/hour PP
50 lbs/hour PET
60 lbs/hour ABS
60 lbs/hour PVC

VACUUM FORMING

70 lbs/hour HDPE & LDPE
70 lbs/hour PP
200 lbs/hour PS
250 lbs/hour PVC

 

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:

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.

 

Congratulations Graduate !


Thank you for taking the time to go through our PolyScience Cool School we hope we have been informative and educational. If you need any more information we are always available to answer question and give advice on the best purchase for your company. Contact us at .

 

 

 

This is to certify that___________________________
has successfully completed PolyScience’s Cool School and is now an informed and educated customer.

 

Date_____________________