Issues with the total heat transfer area and effective heat transfer area displayed by the HTRI software
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I have some doubts regarding the heat exchange area calculated using the HTRI software, and I would appreciate it if experts could give me some advice. It is known that there are 600 heat exchange tubes, with a length of 2.5 m, an outer diameter of 19 mm, and a wall thickness of 2 mm. It is a conventional BEM-type heat exchanger, with tube sheet thicknesses of 65 mm at both ends, and a tube end protrusion height of 1.5 mm from the tube sheet. According to the calculations. 1. Manual calculation: Using 600 bare tubes, the heat exchange area is calculated as 3.14×(19/1000)×2.5×600 = 89.49 m2. HTRI shows 89.535 m2. 2. Manual calculation: By deducting the length of the tube ends that protrude and the thickness of the tube sheet, the effective heat exchange area is determined; in this case, the effective tube length is 2500–65×2–1.5×2 = 2.367 m. Thus, the heat exchange area is 3.14×(19/1000)×2.367×600 = 84.73 m2, while HTRI shows 87.207 m2. I’m not sure which value is used in HTRI’s internal calculations; I’m uncertain about this margin for heat exchange because I don’t know which heat exchange area the software uses for its calculations
When calculating the heat transfer area, the HTRI software generally takes the total external surface area of the entire tube into account as the overall heat transfer area, which includes both the bare tube portion and the part of the tube end that protrudes from the tube sheet. However, the specific calculation model may still undergo some adjustments or modifications to meet different design requirements and heat transfer effects. Therefore, there is a difference between the effective heat transfer area indicated by HTRI (87.207 m²) and the effective heat transfer area calculated manually by you (84.73 m²); this may be due to the use of a specific algorithm within the software or the consideration of additional factors related to heat transfer. Typically, the calculation results produced by the software are optimized and adjusted; if there are any doubts, one can refer to the user manual provided by the software or seek technical support for an explanation of the specific calculation methods and the way in which heat exchange areas are handled. In design and engineering applications, the computational results of software can serve as an important basis, but comprehensive consideration must also be given to actual conditions. .
3.14 vs. the value of Pi (Π)
Is the tube sheet thickness determined by you or the one specified in HTRI? Generally, the effective area is used, as the tubes in the tube sheet section are not involved in heat exchange