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ABSTRACT
This paper deals with various issues on testing heat exchangers at cryogenic temperatures, the test setup and experimental studies on perforated plate heat exchangers. A number of fluid flow circuits are used in practice for testing a heat exchanger at cryogenic temperatures. These circuits are reviewed and a simplified fluid circuit is proposed with justifications. Effects of the fluid inlet/outlet tubes on the performance evaluation of the heat exchanger were investigated numerically. It is found that convection heat transfer between fluid and the tube as well as conduction heat transfer through the tube walls can cause significant errors in the evaluation. These errors are considered while designing the inlet/outlet tubes for the test setup. Details of the test setup including mounting of temperature sensors, instrumentation and data acquisition are discussed. Some selected data from our experimental studies on perforated plate heat exchangers are presented. Transient study on the heat exchanger by using the setup is also demonstrated. For pressure drop studies, a separate test setup is used.
Nomenclature
| Cp | = | specific heat at constant pressure, J.kg−1.K−1 |
| C1,C2,Cμ | = | constants |
| Cu | = | copper perforated plates |
| E | = | constant |
| H | = | channel height, m |
| ID | = | inner diameter |
| K | = | Von Karman constant |
| k | = | turbulence kinetic energy, m2.s−2 |
| kth | = | thermal conductivity, W.m−1.K−1 |
| L | = | tube length, m |
| Lh | = | latent heat of vaporization of liquid nitrogen, J.kg−1 |
| LN2 | = | liquid nitrogen |
| = | boil-off rate of liquid nitrogen, kg.s−1 | |
| = | mass flow rate, kg.s−1 | |
| N | = | number of plates, dimensionless |
| OD | = | outer diameter |
| P | = | pressure, Pa |
| Pr | = | Prandtl number, dimensionless |
| PPHE | = | perforated plate heat exchanger |
| PT | = | pulse tube |
| Q | = | heat flow, W |
| = | heat flux, W.m−2 | |
| r | = | radius, m, also radial direction |
| s | = | width of the fluid separating wall, m |
| SS | = | stainless steel |
| T | = | temperature, K |
| t | = | time, s |
| U* | = | mean velocity at a point in the viscous sublayer in non-dimensional form |
| u | = | velocity component in x direction, m.s−1 |
| υ | = | velocity component in r direction, m.s−1 |
| W | = | channel width, m |
| x | = | axial direction |
| y | = | radially inward direction from the wall |
| y* | = | distance from the wall to a point in the viscous sublayer in non-dimensional form |
| yP | = | distance from the wall to a point P in the viscous sublayer, m |
Greek symbols
| α | = | thermal diffusivity, m2.s−1 |
| ϵ | = | effectiveness, dimensionless |
| ∈ | = | turbulent energy dissipation rate, m2.s−3 |
| ∈ H | = | thermal eddy diffusivity, m2.s−1 |
| ∈ M | = | momentum eddy diffusivity, m2.s−1 |
| μ | = | dynamic viscosity, Pa.s |
| ν | = | kinematic viscosity, m2.s−1 |
| τ | = | shear stress, Pa |
| ρ | = | fluid density, kg.m−3 |
| σk, σ∈ | = | constants |
Subscripts
| c | = | cold fluid |
| cin | = | cold fluid inlet |
| cout | = | cold fluid outlet |
| h | = | hot fluid |
| hin | = | hot fluid inlet |
| hout | = | hot fluid outlet |
| M | = | momentum |
| P | = | parameters at point P |
| t | = | turbulent |
| w | = | wall |
Additional information
Notes on contributors
Sukumaramenon Sunil Kumar
Sukumaramenon Sunil Kumar is an associate professor in the College of Engineering Trivandrum, Kerala, India. He received his Ph.D. in Cryogenic Engineering from IIT Kharagpur in 2014. He studied at University of Kerala, India, where he obtained his B.Tech. and M.Tech. degrees. His research interests include cryogenic heat transfer, compact heat exchangers and refrigeration & air-conditioning. He has co-authored 15 papers in archival journals and conference proceedings. He is currently working on analysis of perforated plate heat exchangers used for cryogenic applications.
Tapas Kumar Nandi
Tapas Kumar Nandi is an assistant professor in Cryogenic Engineering Centre, Indian Institue of Technology (IIT), Kharagpur, India. He received his B. E. (Mechanical) degree from North Bengal University, West Bengal, India and Ph.D. from IIT Kharagpur. He worked for the Indian Space Research Organisation (ISRO) as a scientist for about four and a half years. He has been in the teaching profession for the last eighteen years. His research areas include compact heat exchangers, cryogenic refrigeration and liquefaction and cryogenic rocket propulsion.