TY - JOUR ID - 29774 TI - Thermal Design Considerations and Performance Evaluation of Cryogenic Tube in Tube Heat Exchangers JO - Iranian Journal of Chemistry and Chemical Engineering JA - IJCCE LA - en SN - 1021-9986 AU - Saberimoghaddam, Ali AU - Bahri Rasht Abadi, Mohammad Mahdi AD - Department of Chemistry and Chemical Engineering, Faculty of Chemical Engineering, Malek Ashtar University of Technology (MUT), Tehran, I.R. IRAN Y1 - 2019 PY - 2019 VL - 38 IS - 1 SP - 243 EP - 253 KW - heat exchanger KW - longitudinal heat conduction KW - heat in-leak KW - Low temperature' KW - refrigeration DO - 10.30492/ijcce.2019.29774 N2 - Heat exchangers are the most important equipment in refrigeration processes. Design and modeling of heat exchangers operating at low temperatures are different from other regular heat exchangers. This study includes two sections. In the first section, design and modeling considerations needed for evaluating the real thermal behavior of heat exchangers at low temperatures were discussed. These considerations are usually neglected by researchers who have modeled the heat exchanger at low temperatures.  In the second section, a counter current helically coiled tube in tube heat exchanger operating in hydrogen liquefier was modeled and simulated considering notes discussed in the first section. The model was validated compared with the data presented by literature. The results showed the small positive effect of longitudinal heat conduction on hydrogen liquefaction. The heat in-leak into cold fluid resulted in higher cold fluid outlet temperature and higher hot fluid outlet temperature. Simulations showed that the heat in-leak into cold fluid leads to limit the overdesign for cryogenic heat exchangers. A comparison between models with considering different assumptions was presented and showed that the result may vary significantly based on the regarded assumptions. UR - https://ijcce.ac.ir/article_29774.html L1 - https://ijcce.ac.ir/article_29774_95143670834e1b357a6e484b9ef73e91.pdf ER -