Comparison between plate heat exchanger and shell and tube heat exchanger
(1) High heat transfer coefficient.Because different corrugated plates are inverted to form a complex flow channel, the fluid flows in a three-dimensional rotating flow channel between corrugated plates.It can produce turbulent flow under low Reynolds effect (generally re = 50-200), so the heat transfer coefficient is high. It is generally considered to be 3-5 times of shell and tube type.
(2) The logarithmic average temperature difference is large and the terminal temperature difference is small.In shell and tube heat exchanger, two kinds of fluid flow in the shell side and tube side respectively.
The logarithmic mean temperature difference correction coefficient is small, while the plate heat exchanger is mostly parallel flow or reverse flow, and its correction coefficient is about 0.95.The flow of cold and hot liquid in plate heat exchanger is parallel to the heat exchange surface without side flow, so the temperature difference at the end of plate heat exchanger is small. The heat exchange rate of water water can be less than 1℃, while shell and tube heat exchanger is 5℃
(3)Small floor area.The plate heat exchanger has a compact structure, and the heat exchange area per unit volume is 2-5 times that of the shell and tube type.It is not necessary to reserve the maintenance site for pulling out the tube bundle like shell tube.Therefore, to achieve the same heat exchange, the floor area of plate heat exchanger is about 1/5-1/10 of shell and tube heat exchanger.
(4) It is easy to change the heat exchange area or process combination.
As long as several plates are added or reduced, the heat exchange area can be increased or reduced.By changing the plate arrangement or replacing several plates, the required process combination can be achieved and the new heat exchange conditions can be adapted.The heat transfer area of shell and tube heat exchanger is almost impossible to increase or decrease.
(5)lLight weight.The plate thickness of plate heat exchanger is only 0.4-0.8mm, and the thickness of shell and tube heat exchanger tube is 2.0-2.5mm. The shell of shell and tube heat exchanger is much heavier than the frame of plate heat exchanger.Plate heat exchanger is only about 1 / 5 of shell and tube weight
(6) Low price. With the same material and the same heat exchange area, the price of plate heat exchanger is about 40% - 60% lower than that of shell and tube heat exchanger.
(7) Small heat loss.Only the heat transfer plate of the plate heat exchanger is exposed to the atmosphere, so the heat loss can be ignored and no insulation measures are required.The heat loss of shell and tube heat exchanger is large, so it is necessary to keep warm.
(8) Not easy to scale. Because the internal water flow is turbulent and not easy to scale, the scaling coefficient is only 1 / 3 ~ 1 / 10 of that of tubular heat exchanger.