Feasibility study for replacing the heat source based on the existing heat exchanger? Help needed
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This post was last edited by *aoshanxn on 2020-4-5 at 18:41. It is known the inlet and outlet temperatures of the cold source; the original heat source was steam, but it has now been changed to condensate as the heat source. It is necessary to determine whether the existing heat exchanger area is sufficient to meet the required outlet temperature of the cold source Is it possible to calculate this simply by using Qh=Qc to determine the temperature at the outlet of the heat source, and then using Q=KAT (with the heat transfer coefficient being determined based on the original operating conditions) to find the required area A’ of the heat exchanger? I’m not sure if this approach is feasible
The original heat source outlet was liquid condensate, and latent heat was involved in the heat exchange process. By using liquid condensate instead, the heat exchange now involves only temperature changes. It’s not impossible to do this, but a large amount of liquid condensate is required, which results in too fast a flow rate of the condensate within the heat exchanger. Additionally, when both steam and liquid condensate are used as heat sources, in shell-and-tube heat exchangers the diameters of the tubes vary, making it difficult to calculate the heat transfer simply
Thank you! The original heat source was steam; it has now been replaced by condensate, and it’s certainly necessary to increase the flow rate. As you mentioned, the flow velocity will increase. In such cases, can the heat transfer coefficient K be considered constant during calculations? What do you mean by the difference in the diameter of the tubes you mentioned above? What I need to do now is determine whether the area of the existing heat exchanger still meets the process requirements after replacing the heat source
Thank you! The original heat source was steam; it has now been replaced by condensate, and it’s certainly necessary to increase the flow rate. As you mentioned, the flow velocity will increase. In such cases, can the heat transfer coefficient K be considered constant during calculations? What do you mean by the difference in the diameter of the tubes you mentioned above? What I need to do now is determine whether the area of the existing heat exchanger still meets the process requirements after replacing the heat source
It’s not just a matter of looking at the heat exchange area; the efficiency of heat exchange also matters. The heat transfer coefficient can vary, and different pipe diameters result in different heat transfer efficiencies. I worked on a project where I wanted to use an existing steam heater as a cooler. The diameter of the tubes in that heater was 19, while the cooler required tubes with a diameter of 15. Even if the heat exchange area met the requirements, it wasn’t sufficient
Different pipe diameters result in different heat transfer efficiencies. Yes, the calculation of the heat transfer coefficient is related to factors such as the pipe diameter and the heat supply coefficient; however, the heat exchanger itself remains unchanged – it is the heat source that changes. I haven’t checked the specific physical property parameters in detail. So, in actual production processes, when conducting evaluations, is it necessary to calculate the heat transfer coefficient? The pipe diameter remains unchanged; the heat source simply changes from steam to condensate, and the flow rate increases. This leads to an increase in the heat transfer coefficient, so it must still be a matter of area
Complete process parameters are needed; otherwise, it’s impossible to help!
It can basically be concluded that it’s not possible.