Process Cooling Magazine

In the April edition of Process Cooling magazine, Group Publisher Anne Armel wrote a complimentary commentary about Lytron’s website. The commentary, titled “Liquid-Cooling Web Site Loaded with Help,” can be found on page 4. It mentions Lytron’s Units Converter and Equation Solver tool, Product Selector tools, Ask an Engineer form, the Cooling Chronicle e-newsletter, and our blog. (Thanks Anne!)

Worm Drive Hose Clamp

Lytron frequently receives questions through its “Ask an Engineer” website form. A customer recently asked us the following question: “What is the recommended connection mechanism for heat exchanger tubing with the ‘BD’ designation?”

A beaded (BD) fitting is generally specified when a system requires flexible hoses. The bead prevents the hose from slipping off the cold plate’s or heat exchanger’s tubes while a clamp prevents leaks at the joints. Lytron recommends two types of clamps for the BD fitting: the ear/pinch clamp and the worm/gear clamp.

The pinch clamp is a metal band that is crimped with a special tool. This is the best choice since a pinch clamp can withstand vibration and temperature changes over time without loosening up. Pinch clamps as well as other more sophisticated clamps are available from McMaster-Carr in its “Hose and Tube Clamp” catalog section. The worm clamp consists of a notched band with a screw mechanism to loosen or tighten it. Worm clamps are available at a local hardware or automotive parts store. Lytron’s application note “Fitting and Hose Clamp Selection for Cold Plates and Heat Exchangers” provides more details.

 For OEMs, Lytron can provide custom cold plate or heat exchanger assemblies that include hoses and/or fittings.

 John, Engineer

Flat Tube Heat Exchanger

Lytron frequently receives questions through its “Ask an Engineer” website form. A customer recently asked us the following question: “Do your standard heat exchangers, specifically your ES505G24 heat exchanger, require any specific filtration?” Filtration of the coolant will depend on how clean it is. On the liquid side, the largest acceptable particle size for the liquid path is around 0.03″ (or 750 um). In addition, you should ensure that your coolant is clean in order to help minimize the risk of corrosion. For example, if you are using an ethylene glycol and water solution you’ll want to ensure that the water meets the minimum requirements for good quality water.

It is also important that dust and dirt do not clog the fins on the airside. If you are in a relatively clean room indoors, you probably won’t need a filter; however, you may need to clean the heat exchanger periodically to remove dust build up. Our application note on recirculating chiller tune ups shows a picture of what a very dusty heat exchanger/condenser looks like and contains information on how to clean a heat exchanger’s fins.

EGW Wordle

Many customers ask us what concentration of ethylene glycol we recommend they use in their chillers, cooling systems, and/or liquid cooling loops. It depends quite a bit on your thermal and mechanical requirements, such as required thermal performance, how often you replace your fluids, if you are concerned about corrosion, etc. For most applications, however, we recommend using a solution consisting of 30% ethylene glycol and 70% water (EGW). Water has the best thermal performance, while the inhibited glycol provides freezing point suppression and corrosion protection.

When higher concentrations of glycol are used, it can cause problems within your cooling loop. Over time, the concentration of glycol will increase due to evaporation of water from the system. When the glycol concentration is too high, glycol will collect in pump seals forcing them apart and creating a leak path.

What concentration of glycol are you using? Have you experienced any problems in the past because of your glycol concentration? Please share your experiences.

Tube-Fin Heat Exchanger

Lytron frequently receives questions through its “Ask an Engineer” website form. A customer recently asked the following question: “While using your heat exchanger selector tool, a warning popped up stating that “Most heat exchangers have a maximum allowable flow rate of 2 GPM.” I was curious as to why 2 GPM is the highest. What are the limiting factors?”

Most standard heat exchangers are designed to operate with a flow rate between 1 gpm and 4 gpm. Increasing the liquid flow rate beyond the optimum range will not necessarily improve the performance of the heat exchanger. What will happen is the heat exchanger will become air-side limited, which means that a much larger fan may be required in order to continue to increase performance. In extreme cases, a commercial off-the-shelf fan will not be adequate to increase the airflow enough to balance the thermal performance. Refer to Lytron’s Integrating a Heat Exchanger into your System: Fan Considerations for more detailed information.

In addition, Lytron’s standard heat exchangers are designed with 3/8″ OD x 0.028″ wall thickness. For many of the smaller heat exchangers, increasing the liquid flow rate much beyond 2 gpm will substantially increase the liquid side pressure drop through the heat exchanger. This means you will need a much larger pump for your cooling system.