Tacking heat-transfer in refrigeration an onerous task, says academic
Uttar Pradesh, India, 14 April 2019: Tackling heat-transfer within the scope of refrigeration, poses its own set of challenges. Dr Jahar Sarkar, Associate Professor, Indian Institute of Technology, Varanasi, in the central Indian state of Uttar Pradesh, said that secondary refrigerants, such as brine fluids, will have a low heat transfer and a high pumping power due to high-viscosity, which leads to a pressure drop. Within the scope of brines, Sarkar added, the brine made of calcium chloride is comparatively the best and is also the more commonly used secondary refrigerant. Supercritical carbon dioxide (sCO2), he said, is a good option and is used in supermarket installations; however, the operating pressure for sCO2 is high. However, he said that there are other non-aqueous options, which are also cost-effective.
Ice-slurry, Sarkar said, is one option for heat-transfer. “Supermarkets that use ice-slurry — the mixture of water, ice and ethanol – have also been evaluated in European countries,” he said. Gas hydrate-slurry, he said, is another promising secondary refrigerant; however, it is still under research and development. The numerous options available in the scope of secondary refrigerants, Sarkar highlighted, makes it difficult to choose the best option, as they all have advantages and disadvantages.”
While giving an update on the situation with regard to the use of refrigerants in India, Sarkar said that today, there are a number of products equipped with eco-friendly refrigerants — hydrocarbons, used in supermarket installations. However, the phase-out process of refrigerants having a high global warming potential (GWP) is slow, as compared to developed countries.