Recirculating Chiller Options and Fluid Compatibility

Chiller Options for Advanced Requirements and Specialized Applications

Recirculating chillers are liquid cooling systems that offer precise temperature control and/or cooling below ambient temperatures (Figure 1). Chillers have many options so that they can be easily integrated into a wide variety of applications. These recirculating chiller options include special application options, fluid compatibility options, protection options, and convenience options.

Special applications and fluid compatibility chiller options, featured below, include a heater, internal insulation package, low temperature operation, water-cooled condenser, and 0.1°C set point

Heater

When the ambient temperature is below your required chiller set point temperature, a heater may be needed. This option is especially helpful when equipment is turned off nightly or turned on and off in a cold environment. The heater option is a submerged 2000 W, 230V electric resistance heater that allows a set point temperature to be reached faster during cold start-ups or during frequent coolant set point cycling. It has a built-in over temperature (non-adjustable) shut-off. When the coolant is within 3°C of the set temperature, the heater shuts off and the refrigeration cycle takes over until the set temperature is reached. This option is available on Aavid’s RC011 to RC045 models. It does not extend the coolant temperature range.

Internal Insulation Package

An internal insulation package greatly reduces the formation of condensation on the tank, pump head, and coolant lines when the chiller coolant set temperature is below the ambient dew point. It helps prevent corrosion within the chiller as well as damage to electronics from drips. An internal insulation package is recommended for applications where the set temperature is 10°C or less as well as when the ambient temperature is above 25°C.

Low Temperature Operation

For low temperature set points (-5°C to 25°C), the low temperature operation option maximizes performance and provides more low temperature cooling capacity than a standard chiller. An internal insulation package is required when selecting this option. Low temperature operation is used in lasers, x-ray cooling, analytical instrumentation, and more.

Water-Cooled Condenser

Another option is a water-cooled condenser. This option allows for rejecting heat to an external liquid coolant source via a brazed plate liquid-to-liquid condenser instead of rejecting it to ambient air with a liquid-to-air condenser. This option prevents room warming and possible air conditioning overload. Also, water-cooled chillers are quieter because there is no condenser fan. The liquid coolant source is typically facility water, but it can also be another chiller located in a different room. The chiller cooling capacity is based on a facility water temperature of 75°F (24°C) at a pressure less than 100 psi. Figure 2 shows the recommended facility water flow rates for each Aavid recirculating chiller. Contact Aavid’s applications engineering for required facility flow rates at different temperatures.

Figure 2: Recommended Facility Water Flow Rates for Aavid Recirculating Chillers

Model	Flow Rate (min)
RC011	1.4 gpm
RC022	1.4 gpm
RC030	1.9 gpm
RC045	3.4 gpm

0.1°C Set Point

With a standard chiller, the user can set the temperature to the nearest degree. With the 0.1°C set point option, temperature can be set to the nearest tenth of a degree, allowing for more precise control of the coolant delivery temperature. It is only available in Celsius. This feature is recommended when temperature stability is critical. Laser cooling and analytical instrumentation cooling are two applications for which this option might be selected.

Fluid compatibility options include a deionization (DI) water cartridge, high purity plumbing, and PAO compatibility.

Deionization Water Cartridge

A DI water cartridge removes ions from the coolant, maintaining a fluid resistivity level between 1- 3 Megaohm/cm by partial flow through the resin bed. The filter cartridge is externally mounted on the return to the chiller. High purity plumbing should be selected with this option due to the corrosivity of deionized water. The filter should be replaced every 3-6 months with normal operation. Resistivity can be tested to determine if the cartridge should be replaced sooner. (This option does not include a resistivity indicator light and is not available with centrifugal pumps.)

High Purity Plumbing

With the high purity plumbing option, all wetted components are fully compatible with DI water. High purity components include a nickel-brazed evaporator, a stainless steel positive displacement pump, and nickel-plated or nylon fittings. The high purity plumbing option is strongly recommended when selecting a DI water cartridge.

PAO Compatibility

Standard chillers typically use filtered water and inhibited ethylene glycol and propylene glycol water solutions. However, polyalphaolefin can be used as a coolant as well. Polyalphaolefin (PAO) is a heat transfer fluid used frequently in military and aerospace industries for its dielectric properties and wide range of operating temperatures. When using this fluid, the appropriate wetted materials must be selected. The PAO compatibility option includes a ½ HP centrifugal pump, brass fittings, push lock hose, 5-micron oil filter, anti-siphon system, and internal insulation package. The PAO compatibility option is available only on the RC011, RC022, RC030, and RC045 recirculating chillers.

There are many options available with recirculating chillers. Coolant compatibility and temperature control options are just a few of them. Understanding the options available on a chiller is important in determining how a chiller will meet your application's specific liquid cooling needs.