https://orcid.org/0000-0002-8670-7351
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ABSTRACT
In this study, implementation of a thermosyphon heat exchanger into a Stirling refrigeration system is demonstrated by means of both theoretical and experimental analyses. R-134a was employed as the working fluid which formed a liquid column at the condenser exit, enabling a two-phase flow through the evaporator. Experiments were conducted in a controlled chamber. Cooling capacity, coefficient of performance, and two-phase pressure drop of the cooler were compared at two different voltages. The flow regime for the refrigerant in the evaporator was found to be stratified based on the calculated wavy flow and Lockhart–Martinelli parameters.
Nomenclature
| A | = | area, m2 |
| COP | = | coefficient of performance |
| d | = | diameter, m |
| e | = | specific energy, kJ/kg |
| E | = | energy, kJ |
| f | = | friction factor |
| F | = | shear force, kg.m/s2 |
| Fr | = | Froude number |
| g | = | gravitational acceleration, m/s2 |
| G | = | mass flux, kg/m2s |
| K | = | wavy flow parameter |
| L | = | length, m |
| M | = | mass-flow rate, kg/s |
| p | = | pressure, Pa |
| q” | = | heat flux, W/m2 |
| q | = | heat transfer rate, W |
| Re | = | Reynolds number |
| T | = | temperature, K |
| v | = | velocity, m/s |
| V | = | volume, m3 |
| w | = | velocity in the z-direction, m/s |
| W | = | power, W |
| x | = | mass quality |
| X | = | Lockhart–Martinelli parameter |
| z | = | axial distance, m |
Greek symbols
| α | = | void fraction |
| Γ | = | evaporation rate, kg/m |
| ε | = | heat exchanger effectiveness |
| μ | = | dynamic viscosity, m2/s |
| ρ | = | density, kg/m3 |
| ΦG | = | Gronnerud multiplier |
Subscripts
| Fr | = | Froude |
| i | = | inner |
| l | = | liquid |
| o | = | outer |
| v | = | vapor |
| z | = | z-component |