Plate Heat Exchangers
Plate heat exchangers are a type of heat exchanger that are built with rigid framed, mounted plates in order to generate parallel flow channels, which allow for the transfer of gases and liquids. The two most common metals used to make heat exchanger plates are aluminum and stainless steel. Stainless steel is a particularly popular choice because of its corrosion-resistance, strength, and ability to withstand high temperatures.
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Applications of Plate Heat Exchangers
The basic type of plate heat exchangers, free from any modifications, are commonly called flat plate heat exchangers. Their goal is to facilitate efficient heat transfer processes for those applications that have moderate levels of material flow and temperature, including many commercial, industrial, and residential applications. Specifically, they are popular for use with the heating, cooling, industrial, and steam processes of HVAC processes, refrigeration, chillers, and domestic water heating processes. For small applications, like work in the hot water sections of combination boilers, manufacturers may employ small, brazed exchanger models. Or, for large, industrial and commercial jobs, manufacturers may use large exchangers with gaskets in between the plates.
Similar to flat plate heat exchangers are plate-fin heat exchangers. In order to perform liquid to liquid heat exchanges, plate-fin exchangers use not only plates but finned chambers as well. Since the fins of plate-fin exchangers are moveable, they may be arranged to exhibit parallel flow, cross flow, counter flow, or even cross-counter flow. Like their cousin, flat plate heat exchangers, plate-fin heat exchangers have a relatively high heat transfer surface area to transfer volume ratio.
Because of this and their ability to create heat transfers with small temperature differences, plate-fin heat exchangers are popular with applications such as nuclear engineering, ammonia production, offshore processing, cryogenic air separation, aircraft cabin air cooling, natural gas liquefaction, and syngas production.
Advantages and Disadvantages of Using Plate Heat Exchangers
Plate heat exchangers offer many perks that types of heat exchangers, such as shell and tube heat exchangers or spiral heat exchangers, do not. For example, they offer a much larger surface area than conventional heat exchangers, which allows for a greater and more efficient transfers of heat, boosted by faster temperature change speeds. Further increasing the surface area offered is the presence of a corrugated surface, which facilitates large single transfers of heat and creates flow disruptions, which cause the fluids to spread out over the plate and transfer their heat faster.
Another advantage of plate heat exchangers is the fact that, by participating in the waste heat recovery, they help manufacturers make their processes more green and cost-effective. In addition, plate heat exchangers typically boast low installation and maintenance costs and minimal upkeep. The extent of plate heat exchanger upkeep usually involves the occasional cleaning of residual traces left behind by some materials. Because they pair such excellent rates of heat transfer efficiency with such a small physical size, plate heat exchangers have made a great splash with domestic heating and hot water flow rates.
Plate heat exchangers are often selected in part for the fact that they do not allow heating and cooling liquids to come in direct contact with each other. They achieve this distinction by having their plates mounted in just such a way that the incoming and outgoing flows run counter to each other. To support this process, heat exchanger plates are usually made from a conductive metal. In addition, to combat the occupational hazards and maintain their shape, rather than buckle under the pressures of flow and temperature changes, the plates must be made of a durable material. Without this strength, they may fall prey to thermal stress and shock. Plate heat exchangers face the risks of thermal stress and shock when one side of the plate is being exposed to cool liquid as the other side is exposed to heated liquid.
Unfortunately, because plate-fin exchangers are so delicate, with such thin channels, they are extremely difficult, even at times impossible, to clean. Also, because of the higher level of detailing required during their fabrication, plate-fin exchangers cost more than most other heat exchangers. These facts somewhat decrease their popularity.
Points to Consider When Purchasing Plate Heat Exchangers
Before settling on a plate heat exchanger to buy, potential customers need to consider a few different things. To begin with, they need to investigate the details of the technologies and plate designs used, as well as the forms of corrugation inside the heat exchanger. There are two types of these corrugations: intermating and chevron. Generally, chevrons offer superior heat transfers. In addition, customers should inquire with their manufacturer as to whether or not they offer maintenance services and, if so, what they are. They should also ask for the specifics of their manufacturer’s parts replacement policy.