Investigation of Heat Transfer Enhancement in the Refrigerator Freezer via Utilizing Elliptical-Shaped Scars

Abstract

The high energy demand in addition to the negative global warming potential effects

that the Refrigeration and Airconditioning equipment are highly contributing lead to

their progressive amendment via the utilization of fluid flow different configurations

control surfaces to achieve a higher freezing efficiency and reduce the power

consumption. Several Researches are conducted on the natural and forced convection

evaporator freezer geometry modification by either of modifying of the compartment

walls or the additional insertion of supplementary flow control surfaces. Due to the

low rate of heat transfer inside the natural convection devices working under hot

climate conditions lead to the adoption of the specified technique to overcome this

problem. In this paper, the insertion of elliptical shape scars of equal dimensions

distributed linearly on the upper and lower inner surfaces of the refrigerator freezer

working under natural convection principle is conducted numerically and tested

experimentally to determine the velocity and temperature of the air taking into

consideration the effect of increasing the scar height and reducing the gaps between

them. The freezer cooling method is modified to the forced convection form by using

an AC axial small fan that rotates at the rear wall at a constant speed of 1500

revolutions per minute. With implementing the shear stress transport turbulence

model in the commercial ANSYS CFX software for a transient time of (15,20&25)

seconds are considered. The simulation results showed that the increased scars height

from (0.5-1.0) centimeters has a positive effect on increasing of the air rotation by a

maximum of (80 percent) in comparison to the improvement in convection heat

transfer for the area with a variable rate achieving a maximum value of (12 per cent)

noticing that the upper freezer scars distribution has achieved a better subcooling

effect rather than the lower surface. Better convergence is reached with test results

ranging from (7-14) %, respectively.