Florine Giraud

Impact of operating conditions on cooling capacity for sorption systems using water as refrigerant

The implementation of compact heat exchanger in sorption systems is a key factor to allow the development of these systems. The aim of this paper is to develop a statistical model with a design of experiment (DOE) methodology and use dimensionless number to evaluate and understand the influence of the height of refrigerant liquid and secondary fluid inlet temperature on cooling capacity of a compact pate-type evaporator for sorption systems working near vacuum pressure. For this purpose, an experimental campaign was conducted on a small adsorption test bench using 13X/water as working couple. Cooling capacities from 640 to 2000 W were measured. The DOE is a Doelhert type with two parameters: the inlet secondary fluid temperature (from 10 to 21 °C) and the filing level of refrigerant in the evaporator (from 6 to 24 cm). Thanks to the exploitation of the mathematical model obtained, optimal points under different constraints were found. A maximum cooling capacity of 2021 +/−75 W in the entire experimental field was predicted for a secondary fluid inlet temperature of 25°C and a height of liquid level of 19.2 cm. Bond number and modified Jacob number per the ratio Psat/Ptriple were analyzed. The dimensionless numbers are correlated to the cooling capacity as a first step for designing compact plate-type evaporator for adsorption systems using water as refrigerant.

Impact of the filling level on the global heat transfer coefficient of a plate cross section for sorption heat pumps

Compact evaporator like plate heat exchangers can play a significant role in reducing the investment cost of low cooling power sorption systems. However, when water is used as refrigerant, the working pressure is very low and vaporization phenomena are really different than vaporization phenomena occurring at higher pressures. Few studies focus on this subject and there is a lack of knowledge about vaporization (boiling or evaporation) phenomena occurring in compact evaporators at low pressure. The design of such evaporators remain manly empirical. There is thus a need of better characterization of the influence of the driving parameters in order to optimize the evaporator design. The objective of this article is thus to go further in the understanding of phenomena occurring in compact plate-type evaporators. In that goal, an experimental campaign was conducted to study continuously the performance of a smooth plate type evaporator as a function of the filling levels. The influence of the saturation press...