Numerical Study on the Effect of Distribution Plates in the Manifolds on the Flow Distribution and Thermal Performance of a Flat Plate Solar Collector

Abstract

Flow maldistribution represents a problem of particular interest in the engineering field for several thermal systems. In flat plate solar collectors, the thermal efficiency strongly depends on the flow distribution through the riser tubes, where a uniform distribution causes a uniform temperature distribution and therefore a higher efficiency. In this work, a Computational Fluid Dynamics (CFD) numerical analysis has been carried out using the commercial software FLUENT ® , in order to determine the flow distribution, pressure drop and hence the thermal efficiency of a solar collector with distribution flow plates inside the manifolds. The obtained numerical solution for this type of thermal systems has been validated with experimental results available in literature for laminar and turbulent flow. Four distribution plate configurations were analyzed. Results show that using two distribution plates in each of both manifolds improves the flow uniformity up to 40% under the same operating conditions when distribution plates are not used. Besides, it is shown that there exists an increase in the overall pressure drop which is practically negligible for the tilt angles commonly employed in the installation of flat plate solar collectors in Mexico. The use of closed end distribution plates on the dividing and combining manifolds allows the thermal efficiency to become close to the ideal thermal efficiency which is obtained with a uniform flow distribution.

Numerical and Experimental Study of Flow Characteristics in Solar Collector Manifolds

“…As boundary conditions for the turbulence model, the hydraulic diameter (D H ) and turbulent intensity (I) at the inlet were prescribed for both models. The inlet manifold diameter was used for the first (D H = D), while the latter was estimated according to the empirical formula [10]:…”

“…Facao [9] studied numerically the flow distribution in a Z-type configuration and proposed the modification of the inlet and outlet tube diameters, aiming to improve its uniformity. Garcia-Guendulain et al [10] analyzed numerically, by means of CFD, four flat plate solar collector configurations and proposed the use of distribution plates inside the inlet and outlet manifolds to improve flow uniformity.…”

“…Facao [9] studied numerically the flow distribution in a Z-type configuration and proposed the modification of the inlet and outlet tube diameters, aiming to improve its uniformity. Garcia-Guendulain et al [10] analyzed numerically, by means of CFD, four flat plate solar collector configurations and proposed the use of distribution plates inside the inlet and outlet manifolds to improve flow uniformity.In light of the above, the present paper presents a study of the flow characteristics in the manifold of a Z-type solar collector. Both experimental measurements and numerical simulations are carried out and their results are compared to each other.…”

Optimization Of The Flow Distribution In V-Groove Flat Plate Solar Collector using Cfd Simulation

“…To obtain maximum performance, the flow should be equally distributed among the riser tubes that is connecting the inlet and exit manifolds, however, a typical manifold will not provide even flow distribution due to the fluid friction and the sudden branching in the manifold as well as the change in the fluid momentum [2]. The literature is extensively proved that the performance of the FBC is affected by the flow distribution [4], [5] [6]. Quite many parameters are involved in the distribution of the fluid in the collector such as fluid mass flow rate, collector tilt angle, and flow direction.…”

“…Quite many parameters are involved in the distribution of the fluid in the collector such as fluid mass flow rate, collector tilt angle, and flow direction. Juan et al [6] found that the high flow rate increase flow misdistribution due to increased inertia effect. Jianhua et al [7] found that the collector tilt angle negatively influences the flow distribution.…”