Custom Cooling System Economics
Figure 1: Ambient Cooling
System Internal View
Cooling systems, including compressor-based chillers, liquid-to-liquid cooling systems, and ambient cooling systems, can be purchased as standard products "off-the-shelf", modified from existing standard systems, or completely custom designed to meet your unique needs. By working with a manufacturer that has a large number of standard technologies available, as well as significant experience designing custom systems, you'll be able to modify a standard cooling system or design an entirely custom cooling system with a better value proposition. If a standard cooling system or a slightly modified standard cooling system will meet your needs, you'll generally save over designing an entirely custom system. However, if a modified or custom cooling system is what you need, involving your manufacturer early in the design process and reviewing the cost drivers is important since the costs can vary quite a bit.
With custom cooling systems, the non-recurring engineering required to meet design specifications can be a significant up-front cost. Some of the specifications that can contribute to engineering materials and assembly costs include the type of cooling system, custom versus standard internal components, the locations and spacing of the internal components, controllers for numerous sensors and instrumentation, special power requirements, compatibility with specific coolants, and agency approvals.
Figure 2: Custom Liquid-to-Liquid
Ambient Cooling System, Liquid-to-Liquid Cooling System, or Recirculating Chiller
An ambient cooling system, or modular cooling system (MCS™), will provide reliable cooling for applications where precise temperature control and cooling below ambient temperature are not required. An MCS consists of a high performance heat exchanger integrated with a fan, pump, and tank in a durable metal chassis. (See Figure 1.) A standard MCS can handle up to 3.5 kW. A liquid-to-liquid cooling system (LCS™) also has a heat exchanger, pump, and tank within a chassis. However, an LCS offers precise temperature control of process water and transfers waste heat to facility water via a liquid-to-liquid heat exchanger. (See Figure 2.) If facility water is not available and precise temperature control or cooling below ambient temperature is needed, the best solution is a Kodiak® recirculating chiller. (See Figure 3.)
A standard LCS and a recirculating chiller are similar in costs, depending on the sizes and options selected. However, a standard recirculating chiller offers up to 6kW of cooling, whereas a standard LCS offers up to 22kW. (To compare heat load and set point temperature and how these impact the selection of a cooling system, see Figure 4.) Regardless of the type of cooling system, if you determine that a modified standard or custom cooling system is what you'll need, it is important to note that there will probably be a minimum order quantity required by the manufacturer.
Custom Internal Components
Figure 3: Kodiak Recirculating Chiller
Even in custom cooling systems, virtually all of the internal components are standard products. With a wide variety of heat exchangers, pumps, tanks, and fans on the market, it is rare that there is not a component already designed and built that will work for the cooling system. If a custom internal component is needed, there are additional engineering design and manufacturing steps involved in the process and hence additional costs. (See "Heat Exchanger Manufacturing Cost Drivers " for more information on custom heat exchangers.)
Locations and Spacing of the Internal Components
Unlike the rare requirement of a custom internal component, a common requirement for custom cooling systems is finding a way to pack more and more cooling into smaller and smaller spaces. This can be accomplished by packing the components more tightly and/or by selecting smaller components that are more efficient. The tighter or more densely packed the components are within the chassis or cooling system package though, the more challenging it is to design and manufacture. (Sometimes the more compact it is the more difficult it is to service too.) With more tightly packed components, there is less airflow and therefore less performance. In turn, a more powerful fan or better performing heat exchanger may be required. Also, as component locations or spacing are changed, pressure drop needs to be looked at along with connections and other design elements to ensure a reliable product that meets or exceeds expectations.
Controllers for Sensors and Instrumentation
Figure 4: Heat Load vs.
Set Point Temperature Chart
Controllers provide numerous ways to monitor the cooling system by a display or data output to a remote computer. The standard recirculating chiller controllers offer digital temperature display, calibration offset, low flow shut-off, auto-restart, °C/°F toggle, audible alarm, alarm mute, digital pressure sensing, low level, low/high temperature, pressure display, fault shut-off (toggle on/off), and relay contacts. The LCS cooling system controllers offer digital temperature display, °C/°F toggle, over-temperature indicator, calibration offset, low level indicator, low flow indicator, and analog output. If additional sensors and instrumentation are needed, the cost of the controller can rise significantly. In a custom cooling system, a non-standard controller can be one of the most expensive parts. Weighing the costs and benefits of every sensor and instrumentation requirement is highly recommended. For example, in deionization sensing, do you need to know the exact value or do you just need to be alarmed if it reaches a certain point? An alarm is less expensive than output of a precise digital reading. The same goes for flow, pressure, and temperature. For some applications, the additional sensing and instrumentation is well worth the additional cost. It can provide extra protection to the cooling system and to the equipment being cooled, which may be worth thousands or even millions of dollars.
Figure 5: Cooling Systems
Special Power Requirements
As with the controller, it's important to determine if special power requirements for your application are worth the additional cost. The electrical configurations available with the standard cooling systems meet the needs of most applications. (See Figure 5.) They are all single-phase, so three-phase and other options that provide a more universal power configuration (such as being able to operate on both frequencies) will cost more. It may be more cost effective to manufacture two or more types of custom cooling systems that will work for use in separate locations versus manufacturing one that is universal.
Compatibility with Specific Coolants
A standard modular cooling system is compatible with a wide range of coolants, including water, deionized water, oil, and ethylene glycol solutions. The standard LCS is compatible with water, deionized water, and ethylene glycol solutions, and the standard recirculating chiller is compatible with water, deionized water, ethylene glycol solutions, and polyalphaolefin (PAO). If other coolants are required, all wetted materials within the system must be evaluated to minimize corrosion and ensure system performance is optimized. Designing a cooling system to be compatible with other coolants could require additional engineering and non-standard components, such as special tubing or pumps. Compatibility with ethylene glycol solutions or water is generally the easiest compatibility to design in, with PAO and Fluorinert™ compatibility providing more of a challenge and a higher cost.
Another somewhat costly specification is designing a custom cooling system for agency approvals. The standard cooling systems are ETL tested to UL 61010A-1, CE certified, and WEEE compliant. However, ensuring a new design has met agency approvals adds another layer of engineering design and quality control steps, including retesting of custom systems.
The more complex or unusual the cooling system requirements are, the more engineering it will require and therefore the more costly it is likely to be. With custom systems, the engineering time involved to meet specifications is usually a significant initial cost, with non-standard controllers being the biggest recurring cost. The costs of a modified or custom cooling system can vary by thousands of dollars, so knowing the design specifications that impact cost is key. Understanding the types of cooling system available, how standard parts will expedite design and production, when real estate savings may not be worth the money, and which sensors and instrumentation are must-haves vs. nice-to-haves will make a difference. In addition, it's important not to forget that coolant selection, power requirements, and agency approvals come into play as well.