Questions regarding the design, calculation, and simulation of coil-type heat exchangers using ASPEN
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I have some questions regarding heat exchanger design, calculation, and simulation that I would like to ask the experts here. I would like to use ASPEN to simulate coiled or spiral coil heat exchangers, with the aim of obtaining the heat transfer area of these exchangers. The refrigerant flows inside the tubes (under forced convection conditions), while wet air or water flows outside the tubes (under forced or natural convection conditions). However, during the use of ASPEN, it was found that the heat transfer coefficients and heat transfer areas obtained using the DESIGN mode of the HEATX module differed significantly from the actual values. The RATING and SIMULATION modes did not provide any options for designing coil-type heat exchangers; when designing shell-and-tube heat exchangers, forced convection could only be used for both the inside and outside of the tubes, with no option for natural convection. In this case, should I calculate the heat transfer coefficient manually and enter a fixed value for it in HEATX to determine the heat transfer area?
Can this situation of forced convection inside the tube with almost no flow outside the tube, resembling natural convection, be approximated using a shell-and-tube heat exchanger? I’d like to ask the fellow sailors: is it really like this?
HYSYS simulation for spiral coiled tube heat exchangers
Could you please explain in more detail? I’m a beginner with ASPEN and don’t know much about it; I know even less about the software you mentioned.
Can’t use Aspen? Do we have to use HYSYS?
I gave ASPEN a try. It’s really not possible to do it; coil-type heat exchangers should be considered immersion-type heat exchangers, and there’s no relevant module in ASPEN’s EDR. I want to use a shell-and-tube type module, but I can’t select the convective heat transfer mode for the outer and inner tubes. Moreover, coil-type heat exchangers also lack components such as tube sheets and end caps found in shell-and-tube heat exchangers. I wonder if it can be understood this way: a coiled tube heat exchanger is a simplified version of a shell and tube heat exchanger. Since the heat exchange area is large, this type of heat exchanger is chosen in order to fit that area within a smaller housing.
There is a lack of convective heat transfer, I guess. . . . It still cannot be understood as a shell-and-tube type
What is lacking in convective heat transfer? I don’t quite understand.
In the coiled-tube heat exchanger I designed, forced convection occurs inside the tubes, and the same holds true outside them; however, natural convection also takes place in some cases. Is that what you mean?
Right, is it stirring outside the tube, or?
Outside the tube, moist air or water flows across it; however, sometimes the fluid can be considered stationary, so natural convection heat transfer is applied.