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The swirling motion of the fluid retards fouling in the plate heat exchanger. |
Energy derived from waste heat is a sustainable resource and, if properly managed, can remain a renewable source of energy. Advances in the areas of heat exchanger sealing, pressing, strength and efficiency have helped to improve and optimize heat transfer efficiency.
While the means to recover waste heat include a range of equipment, one type often used is heat exchangers. Heat transfer via compact heat exchangers, especially plate heat exchangers, delivers more power per square foot through a close temperature approach, making the technology power efficient.
Plate heat exchangers operate with a smaller temperature differential (ΔT) than many other heat transfer technologies. The close temperature approach in plate heat exchangers allows a high utilization of available temperature difference between the source and the sink. Also, in general, the higher turbulence in a plate heat exchanger results in a higher heat transfer coefficient. Consequently, less heat transfer area is required, and the turbulent flow helps ensure less fouling.
Because plate heat exchangers use less space than other heat exchanger designs, users can install a larger turbine on the same installed footprint. This is directly related to a better utilization of the available temperature difference between the heat source and the heat sink. And, the closer the temperature is, the better.
Compared with other heat exchanger technologies, plate heat exchangers provide relatively easy access for cleaning purposes. Their compact designs require minimal extra floor space for opening and the front panel is accessible. Because a single compact plate heat exchanger normally replaces larger - or even numerous - units, the total effort to access the interior is reduced and requires less manpower. In alternate technologies, the flow is less turbulent; consequently, the risk of fouling may be greater. Other heat exchangers can require more frequent cleaning than plate heat exchangers.
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The close temperature approach in plate heat exchangers allows a high utilization of available temperature difference between the source and the sink. |
In a plate heat exchanger, the corrugated plate design results in high flow turbulence. The resulting high shear stress reduces fouling. As a result, plate heat exchangers normally operate three times longer between cleanings than the technology they are replacing.
Recycled Energy
To get the most from operations, plants can recycle energy for a range of uses rather than producing or buying more - thus reducing fuel consumption and emissions while also reducing operating costs. Compact plate heat exchangers are light in weight, take up little space and can be installed and retrofitted in existing facilities.
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In this diagram comparing shell-and-tube (left) and plate (right) heat exchangers, the dotted lines represent the space required to open and clean the units. |
Many companies are already using compact heat exchangers in their operations. With rising energy costs and environmental concerns, others are considering the technology. Plate heat exchangers can provide features such as optimized heat recovery using less cooling and heating medium, increased cooling or heating capacity using less area and a savings in capital investment and installation due to compact size and light weight. Other potential benefits include lower operating costs with higher heat transfer efficiency, less fouling, less maintenance and increased uptime.
Sidebar:
Evaporators and Condensers
Another benefit of plate heat exchangers is in the way the evaporators and condensers work.
The refrigerant enters the evaporator at the bottom, then quickly flows through the channels to be superheated at the top of the evaporator prior to entering the turbine. The superheated refrigerant leaves the turbine and enters the condenser to be rapidly de-superheated and start condensing. The two-phase mixture condenses completely. The condensed liquid then drains from the heat exchanger channels.
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