HTRI calculates two types of information related to heat exchangers; it’s not clear whether these can be ignored
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As follows, the translation relates to temperature pinch points; there are situations where hot and cold streams intersect in terms of temperature. In previous projects, a design with double-shell series heat exchangers was generally adopted. Since the flow rate in this case is low, a pure counter-current design with a single tube bank and single shell was chosen. Regarding these two suggestions below, I’m not sure whether to pay attention to them or not. Local in-tube temperature pinch detected: Due to thermal stratification effects, a temperature pinch over a portion of the tubewall may have occurred. HTRI methods do not currently account for this condition, and the local mean temperature difference (and hence incremental duty) may be over-predicted. Thermal stratification effects can be reduced by either shortening the tube length to the point where the pinch begins or modifying the process and/or exchange geometry to increase the tubeside velocity. (MN 4128) Temperature pinch predicted in tube pass 1: The localized temperature pinch could effectively nullify up to 41.3% of the tubeside heat transfer surface area in this tube pass. (MN 4126)
Both of these messages are about temperature pinch points occurring within the pipeline. The first recommendation is to shorten the tube length or increase the side flow velocity of the tube in order to reduce the thermal stratification effect. The second warning states that a temperature dead zone may occur within tube bank 1, rendering the heat exchange area on the tube side ineffective, which will affect the performance of the heat exchanger. Although you have chosen a pure counter-current design with a single tube pass and single shell pass, you need to carefully consider these two issues, especially the second warning. It is recommended to conduct a specific analysis and make decisions based on the actual circumstances. .