Help needed – a very basic question regarding heat exchanger design
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I declare that I’m a beginner; I hope the more experienced colleagues will kindly offer their guidance and not laugh at me. When designing a heat exchanger, one must first determine a K value and use this value to calculate the heat exchange area. Then, another heat exchanger is designed, and its K value and heat exchange area are calculated; these values are compared with the previously assumed heat exchange area. If they are roughly similar, that’s fine; otherwise, the design needs to be revised. May I ask whether the assumed K value is determined based on experience or some other factor? Are there any standards or specific methods?
Our K value is obtained from chemical process design manuals, as well as from empirical values. It seems there’s no standard value; let’s see how other sailors determine it
What was said upstairs is correct: the k-value is the heat transfer coefficient, which is determined empirically in advance; after that, the heat transfer area is calculated, and then the specific k-value is derived from the heat transfer area and the amount of heat transferred
Typical K values can be found in chemical handbooks; there is a general range, which you can also use as a guide for making your selection. In the absence of phase transition: the liquid K value ranges from several hundred to several thousand. The gas K value ranges from dozens to hundreds. In the presence of a phase transition: the K value ranges from several thousand to several tens of thousands. All units are w/m2.℃.
The typical K values can be found in chemical engineering handbooks; next, it is necessary to check whether the substance involved in heat exchange undergoes any phase changes. As for the area, I think it’s related to the heat exchange flow rate: lol
First, select a number within a certain range based on empirical data; you can find this information in books on chemical engineering principles or in handbooks on heat exchanger design.
By designing like this, you’re going to exhaust yourself! To design a heat exchanger, 1, you first need to know the load on the heat exchanger (which is determined by the process requirements). 2. The heat transfer coefficient K can be estimated with high accuracy; generally, design firms use this coefficient to determine the theoretical heat exchange area, and adding a margin to it yields the designed area. For details, it's best to consult books on heat exchanger design.
The K value is just one parameter of the heat exchanger; area and the temperature difference between the media also need to be taken into account
It can be found in both the heat exchanger design manual and the principles of chemical engineering; it would be better to read more books before posting
This post was last edited by jia717 on 2009-8-29 at 12:36. It was found in a chemical engineering handbook; if you don’t have an electronic version, I can send it to you····
The K values are based on long-term experience, and there is no standard for them.