Recirculating Liquid-to-Liquid Heat Exchangers Offer an Alternative to Chillers
In many process cooling applications, refrigerated chillers can be replaced successfully with non-refrigerated heat exchange systems.
Non-refrigerated heat exchange systems utilize an existing facility water source to remove heat from the process, providing stable control of temperature, flow rate and pressure while maintaining isolation from your delicate process equipment.
Consider the following questions when trying to determine if this solution will work in your application:
- Are air-cooled refrigerated chillers dumping large amounts of heat into your work area, burdening your climate control system?
- Do you currently use refrigerated chillers with water- cooled condensers but are concerned about the potential for leakage of chemical refrigerants into the work environment?
- Do you currently use an existing facility cooling water source to directly cool your process but worry that it is compromising the performance of your process equipment due to unstable temperature and/or pressure?
- Is the required cooling fluid inlet temperature to your process at or above the facility cooling water temperature?
- Do you require precise temperature control for your process?
- Are there applications for which your cooling water source temperature is too low, resulting in potentially damaging condensation?
- Is your process equipment in danger of becoming damaged due to high facility cooling water pressure?
Maintaining the Heat Exchange System
Unlike air-cooled chillers, for recirculating liquid-to-liquid heat exchangers there are no condenser fins to clean. However, a process coolant filter may be an important option to consider for protecting the system.
If you answered yes to any of the questions above, you should consider a liquid-to-liquid recirculating heat exchange system. The following will discuss the basic features of, and options available for, these systems.
Facility Water. The direct use of facility water or tap water for process heat removal may unburden your climate control system and shorten your chemical list, but there are drawbacks to this practice as well. The inherent fluctuations in temperature, pressure and overall fluid quality (contaminants) are less than ideal for process equipment. Additionally, it is a one-size-fits-all approach because there is no adjustability for temperature or pressure. Liquid-to-liquid heat exchange systems solve this problem by isolating the process coolant fluid and the facility water loops through a brazed-plate heat exchanger while providing a dedicated process fluid temperature control and recirculating system. This ultimately results in precise temperature control for processes that do not require temperatures below that of the tap or building water source.
Heat Removal. Compared to refrigerated chillers, relatively large quantities of heat can be removed in a significantly smaller (as low as 33 percent) footprint. Heat-removal ratings are dependent upon the temperature differences between the facility supply and desired process setpoint as well as the flow rates of both fluids. Unlike refrigerated chillers, gains in cooling capacity always can be achieved if a higher process setpoint can be tolerated or by increasing the facility supply flow rate. The cooling performance is a function of the temperature difference between the facility and process fluids. By allowing a higher process setpoint, you will increase that differential and increase cooling capacity. Likewise, by increasing the flow rate of the facility supply, you will remove more heat from the process.
Precise, Reliable Temperature Control. These systems will supply precisely tempered coolant to your process equipment. A microprocessor-directed PID temperature controller provides a linear output to an electrically actuated, characterized control valve (CCV). This valve varies the facility water flow rate through the heat exchanger to achieve the desired process coolant setpoint temperature. The coolant fluid temperature, therefore, remains stable regardless of any fluctuations in the facility water temperature and pressure. This straightforward yet effective design ensures maximum reliability with minimal downtime. Valve or actuator replacement, if necessary, is quick and relatively inexpensive and does not require specialized certifications or skills as compared to refrigeratedsystems.
Higher Temperature Operation. For applications requiring control at higher temperatures, heating can be added to any liquid-to-liquid heat exchange system. Cartridge heaters are installed into the process fluid reservoir tank or in line for direct immersion in the fluid. These heaters are essentially 100 percent energy efficient. The heating capacity can vary depending upon the specific application. With the heating option, additional reservoir tank level and overtemperature switch safeties further protect the system.
Energy Efficiency. Non-refrigerated heat exchange systems are inherently energy efficient. The pump motor and optional heater are the only components requiring line voltage power. The facility cooling water is conserved due to the characterized control valve passing only the flow that is required to offset the heat load. Without the need for cooling fans or a refrigerant compressor, they are quiet and do not exhaust heated air into the ambient, making them better suited for a range of work environments.
Chiller Features. Features of recirculating liquid-to-liquid heat exchangers are similar to those of refrigerated chillers. Useful options for the recirculating system include a digital-indicating flowmeter, back-flow prevention (anti-siphon) valves, full bypass pressure-relief valve and particle filter. Interface I/O options include remote start/stop input, RS485 serial communications, analog setpoint input, temperature retransmit output and digital status outputs (dry contacts) for temperature alarms, system running, low flow and low fluid level.
So, when the time comes to choose new fluid temperature control equipment for your process, you may wish to consider a recirculating liquid-to-liquid heat exchanger. It just may be the best choice for your process cooling application.