Understanding BPHE efficiency in your systems

SWEP is the world's largest producer of brazed plate heat exchangers (BPHEs). This heat exchanger technology is a great option in terms of efficiency and form factor in multiple applications.  This case highlights how to choose the proper heat exchanger and how that choice directly impacts the performance of the system. 

About 95% of all the material used in the BPHEs structure is also used in the heat transfer process, allowing for a combination of high capacity with a surprisingly compact footprint, heat transfer efficiency and fast response times. SWEP has factories in the USA, Europe and Asia and a product portfolio with more than (30) models of BPHEs for a wide variety of applications and resources.

When it comes to residential heating systems, air conditioning systems, refrigeration systems or industrial applications, it is a given that some heat exchangers will be needed to perform the heat transfer.  A well-dimensioned heat exchanger can guarantee safety, economy, and stability to the process. SWEP, in partnership with ACFC4 Heaters, carried out a study to demonstrate how the selection of the correct heat exchanger directly impacts the overall efficiency of your system.

ACFC4 Heaters offered us its product testing and development bench to analyze the impact of the choice of heat exchangers in a residential heating system with a gas water heater. Evaluating the performance of the system with two different exchangers, it was possible to identify points of optimization and energy savings - even in a small system. It just goes to show that energy efficiency in heat exchangers is a question of choice!

To analyze the impact of heat exchangers on the energy efficiency of water heating systems, SWEP, in partnership with ACFC4 Heaters, carried out a study to compare the performance of 2 different BPHE types on a testing & product development bench. The test bench had a gas heater, an insulated water tank, a variable flow pump with frequency inverter and a set of thermometers and pressure gauges. By comparing the performance and behavior of the E5THx40 and E8THx40 heat exchangers (with the same number of plates, but different dimensions), it was possible to find points of optimization and energy savings when the heat exchanger is optimized (even for small capacity systems).

Despite smaller dimensions compared to the E8THx40, the E5THx40 model was able to guarantee sufficient capacity for the heating system with a small flow rate. For higher flow rates, the E8THx40 tends to exceed the capacity of the E5THx40 due to the larger heat exchange area.

A heat exchanger must be dimensioned and optimized to offer a balance between hydraulic performance, thermal performance, cost of acquisition and operation. On large systems, the cost of acquisition and most operation costs can differ a lot between heat exchangers. 

In the tests performed, it was possible to identify increments of up to 30% in the annual energy consumption between the exchangers. For large capacity systems, the cost of maintaining a pre-determined capacity on badly dimensioned heat exchangers can cost a small fortune.The below graph below shows the impact of the increase in annual electricity consumption (kWh) in relation to the flow rate variation.

The same behavior can be observed by comparing the head losses required for the heat exchanger to operate and the annual electricity consumption (kWh). If the flow of the heat exchanger is under- or over-dimensioned, the head loss varies and directly changes the cost of operation. A greater head loss causes a significant increase in the cost of operation.

 

For an approximate flow rate of 11 l/min, the E8THx40 heat exchanger operates at a higher pressure drop, increasing energy consumption by 40%. In this condition, the thermal load is about 4% lower than the E5THx40. This is because the heat exchanger is operating in a low flow rate condition and does not use its entire operating area efficiently. With both conclusions, it is possible to see that a properly dimensioned heat exchanger, such as the E5THx40, would be a better choice for this range of application.

SWEP’s vast experience in residential heating covers both comfort and tap water heating. Typical applications for our brazed plate heat exchangers (BPHEs) are gas boilers, heat pumps, and solar heating, along with other decentralized heating technologies such as micro-combined heat and power systems and absorption heat pumps. 

Read more about our wide range of heating solutions here.