Abstract
A work on the design and construction of an integrated tetrafluoroethane (R134a) refrigerator-waste heat recovery dryer suitable for use in tropical regions is presented. The system comprises of a refrigerator with its condenser unit retrofitted to serve as the heat recovery mechanism and a drying chamber. The refrigerator had a vapour compression cycle driven by environmentally friendly R134a working fluid (refrigerant). The dryer component was powered by heat dissipated by the condenser piping from the exit of the compressor (superheat region) to the entrance of the sub-cooled region. The maximum drying temperature attained during pre-loading test was 49 °C while the evaporator provided cooling at a temperature of 5 °C. The specific moisture extraction rate of the dryer varied over 0.19–0.22 kg/kW.hr while 150W of cooling was produced at the evaporator in all cases. The energy utilization ratio obtained was 0.92, indicating that 92% of the waste heat recovered was actually utilized. The system coefficient of performance was estimated to be 10.09 thus indicating that the energy derived from IRWHRD was 10 times the energy it consumed. Application potentials therefore exist for use of this dual purpose system for simultaneous production of refrigeration and heating. Storage of food and drying of fabrics make the IRWHRD an option for use in both agricultural development and entrepreneurship development in laundry business.
Highlights
Re-use of waste energy such as rejected heat from a thermodynamic system is an energy conservation measure
It is capable of converting heat at lower temperatures below boiling point of water and its use is increasingly popular for waste heat recovery systems
R134a was chosen for the design due to its low ozone depletion potential (ODP) value of zero and global warming potential (GWP) value of 1300, as against the very high values for most other organic fluids
Summary
Re-use of waste energy such as rejected heat from a thermodynamic system is an energy conservation measure. Waste heat energy can be recovered from a system using various methods They include the organic Rankine cycle (ORC), the Brayton cycle, thermoelectric generator, Kalina Rankine cycle, steam Rankine cycle, and many other advanced technologies [3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13]. Organic Rankine cycle is renowned for its use of organic fluids as working medium instead of steam It is capable of converting heat at lower temperatures below boiling point of water and its use is increasingly popular for waste heat recovery systems. The heat exchanger effectiveness was increased up to 93%
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