No abstract

This paper, an experimental study was carriedout on a dual channel with perforating “V” corrugated absorberthe plate of solar air collector which the air flows both in upperchannel and lower channel of the absorber plate for increasingheat transfer coefficient and improving thermal performance. Theresults of experimental procedures for dual channel withperforating “V” corrugated absorber plate of solar collector werecompared with the flat plate dual channel of the solar collector.Experimental calculations had been performed under Baghdad(33.34° North latitude, 44.4° East longitude) climatic conditions atdifferent values of mass flow rates 0.021 kg/s, 0.027 kg/s and0.32 kg/s. The results showed that the dual channel withperforating “V” corrugated absorber plate of solar collector isfound to perform more efficiently than the flat plate dual channelof the solar collector with an increased 39% in thermal efficiency. Then,it showed that efficiency increases with increasing mass flowrates. Also, it showed that the heat removal factor of the dualchannel with perforating “V” corrugated absorber plate of solarthe collector is 36% more than the flat plate dual channel of solarcollector. At the last part of the study, the exergy relations werederived for both collectors. The results of this part showed that theflat plate dual channel of solar collector is having the largestirreversibility (exergy loss) and the dual channel with perforating“V” corrugated absorber plate of solar collector is having agreatest exergetic efficiency.

Flat-plate collector considers most common types of collectors, for ease of manufacturing and low price compared with other collectors. The main aim of the present work is to increase the efficiency of the collector, which can be achieved by improving the heat transfer and minimize heat loss experimentally. Five types of solar air collectors have been tested, which conventional channel with a smooth absorber plate (model I), dual channel with a smooth absorber plate (model II), dual channel with perforating “V” corrugated absorber plate (model III), dual channel with internal attached wire mesh (model Ⅳ), and dual channel with absorber sheet of transparent honeycomb, (model Ⅴ). The dual channel collector used for increasing heat transfer area and heat removal factor to improve thermal performance. The outdoor test was conducted during the period December (2016) to February (2017) at different mass flow rates 0.0217 kg/s, 0.0271 kg/s and 0.0325 kg/s. The experiments were carried out from 8:30 AM to 3:00 PM for clear days. Experimental results show that the average thermal efficiency was (72.2 %) for model (III), (40.2 %) for model (I), (51.6 %) for model (II), (65.1 %) for model (Ⅳ) and (59.7 %) for model (Ⅴ). At the last part of the study, the exergy analyses were derived for both collectors. The results of this part showed that the conventional channel model (I) is having largest irreversibility, and the dual channel collector model (III) is having a greatest exergetic efficiency.

Experimentally and numerically, the thermal performance enhancement of counterflow twin-pipe heat exchanger with bumpers position variation was explored. A set of semicircular bumpers were positioned at varying distances from the fluid flow entrance on the annulus gap of the concentric pipe heat exchanger (10–70, 70–130, and 130–190 cm). The hot water entered the inner pipe at a constant mass flow rate of 0.0167 kg/s, whereas the cold air entered the annulus gap of a concentric pipe heat exchanger at changing mass flow rates of 2 × 10−5 to 14 × 10−5 kg/s. The numerical portion comprised simulating the efficacy of the heat exchanger with a smooth pipe and varied bumper placements using an artificial neural network (ANN) model. The experimental portion of the present work consisted of a series of tests to determine the optimal position of the bumpers for maximizing heat exchanger efficiency. At a constant fluid inlet temperature and with varied mass flow rates of the cold air, the numerical model was compared to the experimental results. When the bumpers are put at a distance of 130–190 cm, the heat exchanger has the highest thermal efficiency compared to other bumper placements and a smooth pipe. In all cases of the investigation, there is a good correlation between numerical and experimental data.

In this paper, Numerical investigation of the influence of inserting the metal foam to the solar chimney to induce natural ventilation in the test room is analyzed in this work. Two types of solar chimneys which without insertion of metal foam absorber and with insertion of metal foam absorber are designed with dimensions of length× width× air gap (2 m× 1 m×0.3 m) and size of the test room (1.5 m× 1.5 m×1 m). Four incline angles are tested (30 o ,45 o ,60 o ,90 o ) for each chimney and two length of tower inlet (30 cm, 40 cm). ANSYS FLUENT program (version 14.5) used to simulate this model and solve the governing equations by finite volume technique. The results showed that the air flow velocity at the outlet of ventilation solar chimney increases of the model with copper foam absorber about 33% from the model without copper foam absorber at constant inclination angle, therefore this gives indication of the important of insertion the copper foam as an absorber media in the ventilation solar chimney.