ANALYSIS OF A TUBE-FIN 'NO-FROST' EVAPORATORS USING A DISTRIBUTED MODEL
Paulo Henrique Neves Pimenta1; André Luiz Seixlack2
1 Rio Verde University- UniRV; 2 São Paulo State University - UNESP
doi:10.20906/CPS/COB-2015-1057
Resumo
This work presents a numerical model to simulate the flow and heat transfer between the refrigerant fluid and outside air along of tube-fin evaporators commonly used in 'no-frost' household refrigerators. The refrigerant flow inside the tube is taken as one-dimensional and divided in a two-phase flow region and a superheated vapor flow region. The homogeneous flow model is employed for the two-phase flow region. The refrigerant pressure drop and the moisture condensation on the airflow crossing the outside of the tubes are taken into account. The fundamental equations of mass conservation, momentum and energy conservation governing the refrigerant flow are solved in order to evaluate the velocity, pressure and specific enthalpy of the refrigerant fluid, respectively. The energy and mass (humidity) conservation equations for the air flow are solved in order to evaluate the temperature and absolute humidity of the air crossing the evaporator, respectively. The energy conservation equation for the tube wall evaporator is also solved to obtain the wall temperature distribution. The governing equations are integrated numerically using the Euler's method and the resulting algebraic system of equations is solved by the Newton-Raphson's method. The results are compared with experimental data available in the literature and the mean absolute deviation is 2,4 % for the refrigeration capacity and 2,2 °C for the degree of superheat at the evaporator outlet.
Palavras-chave: Tube fin evaporator; Household refrigerator; 'No frost'; Two-phase flow; Distributed model