The efficiency of heat exchange in the water cooler
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Between the hot light ends and the cold light ends of hydrocracking, there is a water cooler; the flow rate of the circulating water is not even one-third of its maximum value. Yet the heat exchange efficiency still results in a temperature difference of around 200 degrees, while in other water coolers the temperature difference is only in the teens or twenties degrees. Why are there such large deviations? Is it due to differences in the design, and what are the advantages and disadvantages of each?
Could it be that frozen saline is being used, or is the heat exchange area very large?
No. All use circulating water. The surface area is similar to that of other heat exchangers.
Is there an air cooler in front? Or the amount of water used is extremely large
There’s no air cooling ahead, and the water flow is only one-third!
Is there something wrong with the thermometer?
The thermometer is fine. The temperature after the back route is similar to the temperature after cooling
I don’t fully understand the statement made by the original poster regarding a \"temperature difference of 200 degrees in the heat exchange effect\" – do you mean that the temperature difference between the inlet and outlet of the hot material is 200 degrees? If that’s the case, there’s nothing strange about it. This can also occur in conventional heat exchangers. For example, even with a temperature difference of 200 degrees for hot materials, the heat load is not high (since no phase change occurs and the enthalpy value is relatively low); therefore, the amount of water required for the circulating water system, based on conventional temperature difference considerations, is also not large. Furthermore, if the system is currently operating at full capacity, it is more likely that the designer of the heat exchanger made a calculation error and chose larger pipes as a safety measure; however, this does not help with heat transfer (after all, when the valves are closed, a lower flow rate results in poorer heat exchange with the medium on the other side due to the larger flow area). If the poster is comparing the water-saving performance of different types of heat exchangers, it is not sufficient to consider only the temperature difference on the hot fluid side; rather, it is necessary to look at the amount of water flow required for heat exchangers with the same tube bundle length but different designs, under the condition that the same process parameters are maintained. (Generally, high-efficiency heat exchange elements have relatively shorter lengths, and the reason for using the same length for comparison is to determine whether different heat loads will arise from heat exchange between the two fluids under the same conditions at the hot and cold fluid inlets.)
Thank you for your answer. I also found information on the calculation of relevant enthalpy values in books. I just don’t understand it – the tubes and other components inside are similar to those in other systems, but it’s possible to cool media at 245 degrees (such as naphtha and certain light jet fuels) down to 45 degrees. It seems unreasonable from a common-sense perspective; could you provide a more detailed explanation?
Q=cm△t. Since the specific heat of water is much higher than that of naphtha, a greater temperature difference is required for naphtha in order to achieve heat exchange equilibrium, right?:lol
However, for other water coolers with similar media, the heat exchange efficiency is only in the teens of degrees. . . I remember there were a ton of formulas when I was in college, but there’s a gap between theory and reality. I wonder if it’s the difference in enthalpy?