Recold / JW Series Fluid Cooler / Freeze Protection
6
For the most part, evaporative closed circuit coolers will be installed for operation on a
RECIRCULATING WATER
The operation of evaporative cooled equipment under approximately full load conditions will prevent freezing of the recirculated water. However, during periods of very little or no heat load when fans and pumps are shut down, some form of freeze protection must be used.
A simple form of freeze protection commonly used is a remote sump tank inside a heated building below the evaporative cooled equipment. The water circulation pump is located at the remote tank circulating water through the evaporative cooler during load conditions. When the unit is shut down, the water drains down into the remote sump tank which is in a heated atmosphere.
The remote sump installation may be unacceptable in some cases due to unit location or space limitations. For these applications, pan water freeze protection may be attained by means of an optional electric heater located inside the unit pan. Electric pan heaters are designed to prevent pan water freezing during unit shut down with fans and pumps idle.
Water lines to and from the unit, pump, pump discharge and drain lines must be wrapped with a
Table 1 Glycol Flow Correction Factors
Unit Model | Ethylene |
|
|
| Design Flow GPM |
|
|
| |||
Glycol |
|
|
|
|
|
| |||||
|
|
|
|
|
|
|
|
| |||
JW/JWL |
|
|
|
|
|
|
|
|
| ||
By Volume | 40 | 50 | 70 | 90 | 100 | 125 | 150 | 175 | Above | ||
| |||||||||||
|
|
|
|
|
|
|
|
|
|
| |
| 20% | 1.07 | 1.05 | 1.02 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | |
10A thru 35C | 30% | 1.10 | 1.07 | 1.02 | 1.01 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | |
40% | 1.14 | 1.11 | 1.05 | 1.01 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | ||
| |||||||||||
| 50% | 1.16 | 1.13 | 1.06 | 1.01 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | |
| 20% | 1.12 | 1.09 | 1.05 | 1.03 | 1.02 | 1.00 | 1.00 | 1.00 | 1.00 | |
50A thru 50C | 30% | 1.16 | 1.12 | 1.07 | 1.04 | 1.02 | 1.00 | 1.00 | 1.00 | 1.00 | |
40% | 1.19 | 1.16 | 1.11 | 1.06 | 1.04 | 1.01 | 1.00 | 1.00 | 1.00 | ||
| |||||||||||
| 50% | 1.23 | 1.21 | 1.14 | 1.08 | 1.05 | 1.01 | 1.00 | 1.00 | 1.00 | |
| 20% | 1.15 | 1.11 | 1.09 | 1.06 | 1.04 | 1.03 | 1.01 | 1.00 | 1.00 | |
70B thru 130C | 30% | — | 1.18 | 1.11 | 1.07 | 1.05 | 1.03 | 1.01 | 1.00 | 1.00 | |
40% | — | 1.20 | 1.15 | 1.10 | 1.07 | 1.05 | 1.03 | 1.00 | 1.00 | ||
| |||||||||||
| 50% | — | 1.23 | 1.20 | 1.11 | 1.11 | 1.07 | 1.04 | 1.00 | 1.00 | |
HEAT EXCHANGE COIL PROTECTION
The best means of heat exchanger coil freeze protection is to circulate an ethylene glycol water solution. The solution freeze points with respective ethylene glycol by volume are given in Table 11 below. This method will allow freeze protection irrespective of heat load or unit shut down.
Some applications will not permit the use of an ethylene glycol solution. Under these circumstances, other means of freeze protections must be used and the following rules strictly adhered to.
1.Maintain full flow through the coil
2.Maintain heat load on the coil at all time so that the leaving water temperature does not drop below +50°F
Full flow alone will not protect the coil. Temperature of +50°F must also be maintained.
Methods of maintaining the recommended fluid temperature may vary with system design and operation. A simple means of preventing heat loss may be to locate the unit indoors allowing a heated atmosphere. Adequate space and ductwork must be provided for proper operation.
Units operating in low ambient conditions with a heat load which becomes very low or drops off completely may require the addition of an artificial load to maintain safe fluid temperature. The amount of artificial load required may be reduced by means of discharge positive closure dampers. The addition of the dampers will prevent induced air circulation or the chimney effect which may occur during unit shut down.
The above methods of coil freeze protection, when properly applied and maintained will provide good equipment protection. All methods, other than those using an adequate antifreeze solution, should provide a means of emergency coil draining. It is recommended that automatic drain valves and air vents with vacuum breakers be installed on each coil circuit. Adequately size drains with
Freeze |
| Ethylene Glycol (by volume) |
| ||
|
|
|
| ||
20% | 30% | 40% | 50% | ||
Point °F | |||||
14 | 3 | ||||
| |||||
