Selection of heat exchanger K

This post was last edited by wiseboy on 2018-3-26 at 17:10. The recommended values are merely very rough estimates, and no one accepts them these days. It’s based on calculations, provided that you do them correctly. Based on the data table you provided, it seems your calculations are pretty accurate. These days, project owners simply don’t bother to pay attention to you when it comes to recommendation scores.

Oh, thank you. I told you; the actually calculated K value differs significantly from the one recommended in the manual.

I wonder what proportion of steam in a typical steam heat exchanger condenses into condensate after heat exchange; it’s hard to determine

This post was last edited by wiseboy on 2018-3-29 at 11:54. There are no real problems; check your heat exchanger. Many heat exchangers not only achieve complete condensation but also supercool the liquid. For example, at normal pressure and 100°C, the steam not only condenses completely but the condensate also cools down to 70°C (supercooled). But your heat exchanger can also condense 30%, with 70% remaining as steam: everything is controllable when designing the heat exchanger. Wish you progress in your studies and broader insights.

So, how is the K value of a heat exchanger typically determined? Is it feasible to choose it by comparing with heat exchangers in similar operating conditions? In actual production, there is a large margin in heat exchangers; we have a set of falling film evaporators, and keeping the heating steam pipeline at less than 50% capacity is sufficient to meet the requirements. According to the process design manual, my calculations show that there is still a significant gap. I have no idea how to do it

This post was last edited by wiseboy on 2018-3-30 at 16:51. In the past, rough estimates and careless calculations were often used in heat exchanger design, resulting in a high degree of excess capacity in these heat exchangers; but that is history now. With the advancement of science and technology, heat exchanger designs are now more scientific, and the phenomenon of excessive capacity is gradually decreasing; however, rough estimates and careless calculations still occur. In modern specialized design, the degree of design richness is generally set at 10% to 30%. As for how the K value of the heat exchanger is generally selected, that is also a matter of historical precedent. The K value of heat exchangers is now calculated; using a predetermined K value is outdated, and no one accepts the K value that you choose anymore. Those who choose K can only lose users' trust. Referring to K as “making things up on the spot” is obviously a joke, and it’s not in line with the pace of the times.

There is a practical observation: in normal evaporators or coolers, the opening degree of the steam control valves or circulating water control valves during actual operation is always below 50%. Does this mean that the excess capacity of the heat exchanger is more than 30%? Please, experts, give me some advice

This post was last edited by wiseboy on 2018-3-31 17:12. I already said that there are those who are several times richer. This is a heat exchanger design without a blueprint. It’s today – there are countless homeowners who, in order to save a little on design costs, choose not to have any design work done or opt for cheap designs; just take a look at the Haichuan Forum to see this. On Haichuan Forum, there are countless people who pick up sesame seeds and lose watermelons. It can be said without hesitation that when it comes to \"selecting the heat transfer coefficient\", in most cases there is an excessive amount of it; only in very rare cases is it just sufficient due to luck.

The typical recommended values can only be used as a reference, for example, when making a rough estimate of the heat exchange area. However, for designers, a specific design must be carried out based on actual parameters, so that the K value is relatively more accurate.