Design of a recyclic solar air heater for low temperature regions utilizing integrated wavy corrugated thermal energy storage systems

Abstract

This work presents thermal performance prediction of a design of solar air heater for low temperature regions utilizing integrated thermal energy storage systems (PCM unit). Recyclic double air pass is considered for a range of recycle ratio, G = 0–1 at a mass flow rate of 0.01 kg/s. Paraffin wax as a PCM for thermal energy storage is used in two different designs of wavy corrugated PCM unit. Geometrical parameters related to PCM units are considered such as wavelength 0.05≤λ≤0.1m, amplitude 0≤α≤0.015m, length 1≤L≤2m, width 0.5≤W≤1.414m, and height 0.02≤h≤0.04m. Energy-enthalpy method is used to predict the temperatures and phase change of PCM employing finite volume method. Explicit time marching scheme is applied to present transient thermal performance of solar air heater designs. In addition, employed non-orthogonal structured mesh in the complex wavy corrugated PCM units, ensured the numerical accuracy in the prediction. Ambient temperature, Ta and heat flux of the range 5o≤Ta≤20oC and 1000 W/m2 is considered to present realistic situation of low temperature regions, respectively. Thermal backup of 24 h at a significant high outlet air temperature than ambient is aimed to provide in order to support wide thermal applications of solar air heater. The obtained results reported the significantly higher outlet air temperature for the heater design i.e. 9 °C than ambient corresponding to 24 h. Optimum value of different geometrical and flow parameters is obtained as ṁ=0.01kg/s,G=1,λ=0.1m,α=0.005m,L=1.414m,W=1.414mandh=0.04. In addition, presented contours results revealed the associated physics and important guidelines upon the use and size of the thermal energy storage systems in solar air heaters.