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.

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.