Cryogenic pipe flow simulation for liquid nitrogen under steady state conditions
Cryogenics, a thermodynamics study on fluids at temperatures less than 120 K, has many applications in a variety of fields. However, the problem of the high temperature difference between ambient air and temperature of the cryogenic liquid in the transfer line, is...
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| Main Author: | |
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| Format: | Thesis |
| Language: | English |
| Published: |
2019
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/85507/1/FK%202020%2017%20-%20ir.pdf http://psasir.upm.edu.my/id/eprint/85507/ |
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| Summary: | Cryogenics, a thermodynamics study on fluids at temperatures less than 120 K, has many
applications in a variety of fields. However, the problem of the high temperature
difference between ambient air and temperature of the cryogenic liquid in the transfer
line, is a limiting factor. Thus, temperature leakage for heat gain in the transfer
line is of utmost concern. Experimental works can be rather costly and dedicated Computational
Fluid Dynamics (CFD) for cryogenics are limited and require many supporting peripherals. The aim of
this study is to simulate velocity and temperature profiles of line liquid nitrogen using common
CFD package (FLUENT) for fast tracking of flow characteristics of liquid nitrogen (LN2). In
addition, this study numerically investigates the thermal and hydrodynamic performance of
the Vacuum Insulated Pipe (VIP) and Polyurethane (PU) foam insulations by using an
experimentally validated finite volume method (FVM) model. The continuum, momentum and
energy equations are solved in the cryogenic temperature range. The LN2 is assumed as a homogenous
liquid and incompressible at 4 bar operating pressure. The geometry and physics of the liquid
nitrogen flow are axisymmetric for the horizontal transfer line. The simulation model in this
study is solved using the commercially available CFD computational code. This study
numerically investigates single phase heat transfer of LN2 pipe flow for the inlet
volume flow range of 250 to 2000 litre per hour (LPH) at 4 bar operating pressure and 300 K ambient
temperature under steady state conditions. A three-dimensional LN2 pipe flow with k-epsilon
(k-ε) turbulence simulation model has been conducted using CFD ANSYS FLUENT. Both insulator
and jacket pipe layers are created as shell layers where the shell conduction model
predicts the thermal resistance incurred in the presence of multilayers. The axisymmetric
velocity results from the investigation are within the range of 0.44 to 3.39 m/s for inlet volume
flow rates of 250 to 2000 LPH. The temperature distributions resulting from the LN2 pipe flow
simulation with VIP are within the range of 77.0 K to 82.1 K for inlet volume flow rates of 250 to
2000 LPH. The wall heat flux for VIP used for the present study shows the relatively high heat transfer at the wall as compared
to PU foam. In conclusion, the simulation model of LN2 pipe flow successfully developed and shown
an optimum combination of multilayer insulation (MLI) with 20 layers and high vacuum provides the
wall heat flux less than 1 W/m2. The simulation results provide useful insights on the flow field
of
the cryogenic transfer line. |
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