Laminar-flow Liquid-to-air Heat Exchangers – Energy-efficient Display Cabinet Applications

Provisions are stored and displayed in supermarkets and grocery stores, at a temperature lower than the ambient, in display cabinets, which are responsible for a significant amount of the energy use in this sector. During the 1990s, major changes in the regulations governing the use of synthetic refrigerants took place in Sweden. This resulted in many refrigeration systems being converted to systems with indirect cooling by means of a liquid secondary refrigerant. The cooling coil is an important component in a display cabinet and traditionally, different kinds of tube-coils, with aluminium fins on expanded circular copper tubes, have been used. Many secondary heat transfer media have relatively high viscosities at low temperatures, and so the flow regime is often laminar, which may lead to poor heat transfer. However, it is possible to achieve high heat transfer coefficients even for laminar flows if an appropriate design of the heat exchanger is applied. Flat-tube heat exchangers have been used for a long time in automotive applications, where compactness is important. The displa