Questions about overlapping heat exchangers

Some do this to save space in the factory

Some are designed to save space, and others are arranged overlappingly due to issues related to the flow rate of the material inside the heat exchange tubes or the shell.

For hot and cold fluids, there are intersection points in the temperature reduction or increase curves, and it’s not for the reason mentioned by that guy above

This post was last edited by wiseboy on 2012-3-7 09:55. The answer to this question is simple: it is determined by the temperature difference correction factor. It is a mistake to often (by a considerable number of people) treat the logarithmic mean temperature difference as the effective temperature difference for heat transfer. In fact: Effective temperature difference = logarithmic mean temperature difference × temperature difference correction factor, and: Q = KA × effective temperature difference -------------------- This is correct. Q = KA × logarithmic mean temperature difference -------------- This is correct only when the temperature difference correction factor = 1; otherwise it is incorrect! Some people make this mistake their whole lives. When the temperature difference correction factor

Another advantage is the full utilization of the heat transfer medium, but the production efficiency will decrease.

This issue often encounters resistance from the owners, who always think: Why need two small heat exchangers? Wouldn’t a bigger one be better? ? To put it more professionally, property owners often assume that they can do the calculations themselves (by using the logarithmic mean temperature difference, without knowing the temperature difference correction factor). . .

Expert Wiseboy, I believe there are several advantages to using overlapping heat exchangers: 1. As Expert Wiseboy mentioned, due to the temperature difference correction factor, it’s equivalent to having multiple shell circuits, and the advantages were explained in great detail by Expert Wiseboy. 2. Overlapped heat exchangers can be used in a one-in-one-out or multiple-in-multiple-out configuration, enabling switchovers without shutting down the system, which facilitates maintenance. 3. As mentioned on the 3rd floor, for operating conditions characterized by low flow rates and large temperature drops, overlapping heat exchangers are also used in series to increase the flow velocity within the pipes. 4. Saves space. 5. As for the increase in cost, take this as an example: for a unit with a diameter of 900 MM, a length of 6000 MM, and a pressure of 2.5 MPa, operating in 4 flow paths, the area of a standard heat exchanger is approximately 256.6 square units. The weight of a single long-neck flange made of 16Mn alloy is 166.9 Kg. By ensuring a similar flow rate within the pipes, if 4 units are used, each with a diameter of 450 MM, a length of 6000 MM, and a pressure of 2.5 MPa, operating in single flow paths, the area of each standard heat exchanger is approximately 62.5 square units. The weight of a single long-neck flange made of 16Mn alloy in this case is 35.8 Kg; thus, the total weight of the four such flanges is 143.2 Kg. Which price do you say is higher?

How can an overlapping heat exchanger achieve one in operation and one in standby mode, with online switching possible?

One in use and one as backup means two units connected in parallel, switched via valves; it has nothing to do with whether they overlap or not.

The inlet and outlet of the overlapping heat exchanger are equipped with three-way four-position valves that utilize a linkage mechanism to enable simultaneous switching of the inlet and outlet. This allows for the use of both units simultaneously (in summer or when high flow rates are required) or just one unit at a time (under normal conditions). It would be difficult to achieve this without such overlapping design; feel free to contact me for more details.