Double-pass Solar Air Collector Research Articles

Drying of grape pomace with a double pass solar collector

ABSTRACTThis study aims to analyze the performance of a novel design of the double pass solar air collector (DPSAC)-assisted drying system and investigate the drying kinetics of grape pomace which is an agricultural by-product. The samples were dried to a moisture content of 0.01 g water/g dry matter between 100 and 250 min depending on the weather conditions. The average thermal efficiencies of DPSAC were calculated as 79.77, 79.85, and 69.46%. Average values of the coefficient of performance of DPSAC were determined as 5.32, 5.13, and 4.32. The highest specific moisture extraction rate value was achieved as 617.18 g water/kWh. Whereas the mass transfer coefficient (hm) values ranged from 9.15E−11 to 1.04E−7 m/s, the effective moisture diffusivity (De) values were obtained between 3.04E−13 and 1.02E−10 m2/s. The qualitative analysis showed that the drying using DPSAC may be an alternative for drying applications in terms of short drying time and energy usage. Nevertheless, these results clearly suggest a complex and effective interplay between thermal performance and drying kinetics.

Performance analysis of solar drying system using double pass solar air collector with finned absorber for drying copra

Performance analysis of solar drying system using double pass solar air collector with finned absorber for drying copra

Computational fluid dynamical analysis of turbulent flow in a channel equipped with double-pass solar air collector

A numerical analysis is proposed to predict the thermal and flow field for turbulent flow in a double-pass solar collector. The conservation equations are solved by using finite volume method. The k-ω-SST turbulence model is used. The influence of the mass flow rate of air, which changes in range of 0.0139 kg/s and 0.062 kg/s, is chosen as the main parameter. The results show that the flow characteristics strongly depend on mass flow rate of air and the geometry of the double pass solar air collector.

Experimental investigation of a new design solar-heat pump dryer under the different climatic conditions and drying behavior of selected products

The purpose of this research paper is to perform experimental analyses of system in drying of various agricultural products under different climatic conditions. The secondary goals are to keep a constant drying air temperature with PID, to obtain a homogeneous temperature in the drying chamber to determine the effects of PID control on the system, and to evaluate the drying behavior of various products at 50°C a with variable mass flow rate for a drying analysis. Heat energy requirements were provided with new type double-pass solar air collector (DPSAC) and the heat pump (HP) unit while electricity energy requirements were provided with a photovoltaic (PV) system. The coefficients of performance of the whole system (COPWS) for experiments of tomato, strawberry, mint, and parsley were calculated as 1.96, 2.27, 2.28 and 2.17, respectively. The average thermal efficiency of DPSAC was between 16% and 79%. Specific moisture extraction ratio value for the whole system (SMERWS) was varied between 0.03kg/kWh and 0.46kg/kWh for the products. Energy utilization ratio (EUR) was obtained between 0.19 and 0.48. Results demonstrated that the HP unit, DPSAC, PV unit and PID control system can work in coordination with each other and was obtained dried products having good physical properties at the same time.

Design, experimental investigation and analysis of a solar drying system

In this experimental study, a new type solar dryer has been designed and manufactured by using double-pass solar air collector, heat pump and photovoltaic unit. The performance of solar dryer has been tested for carrot drying. In drying system, double-pass solar air collector (DPSAC) has provided the system heat energy requirement for drying process. Constant drying air temperature has been provided with PID (proportional-integral-derivative) control. Carrot slices were dried from initial moisture content 7.76gwater/gdry matter (dry basis) to final moisture content 0.1gwater/gdry matter (dry basis) at 50°C drying air temperature and variable air volume. Velocity of air has been changed depending upon air inlet temperature of drying cabinet. During the drying operation, the air velocity was measured 0.4–0.9m/s. The thermal efficiency of the double-pass collector was calculated from 60% to 78% according to experimental results. Carrot slices were dried at 220min by using double-pass solar air collector in solar-heat pump dryer. Consequently, system (solar-heat pump dryer) can be comfortably operated without the need to the heat pump under normal ambient air conditions.

Analytical and Experimental Studies on the Thermal Efficiency of the Double-Pass Solar Air Collector with Finned Absorber

Problem statement: The design of suitable air collectors is one of the most important factors controlling the economics of the solar drying. Air type collectors have two inherent disadvantages: Low thermal capacity of air and low absorber to air heat transfer coefficient. Different modifications are suggested and applied to improve the heat transfer coefficient between the absorber plate and air. These modifications include the use of extended heat transfer area, such as finned absorber. Approach: The efficiency of the solar collector has been examined by changing the solar radiation and the mass flow rate. An analytical and experimental study to investigate the effect of mass flow rate and solar radiation on thermal efficiency were conducted. The theoretical solution procedure of the energy equations uses a matrix inversion method and making some algebraic rearrangements. Results: The average error on calculating thermal efficiency was about 7%. The optimum efficiency, about 70% lies between the mass flow rates 0.07-0.08 kg sec-1. The thermal efficiencies increase with flow rate and it increase about 30% at mass flow rate of 0.04-0.08 kg sec-1. Conclusion: The efficiency is increased proportional to mass flow rate and solar radiation and .the efficiency of the collector is strongly dependent on the flow rate.

Performance of a double pass solar air collector

Double pass counter flow solar air collector with porous material in the second air passage is one of the important and attractive design improvement that has been proposed to improve the thermal performance. This paper presents theoretical and experimental analysis of double pass solar air collector with and without porous material. A mathematical model has been developed based on volumetric heat transfer coefficient. Effects of various parameters on the thermal performance and pressure drop characteristics have been discussed. Comparison of results reveals that the thermal efficiency of double pass solar air collector with porous absorbing material is 20–25% and 30–35% higher than that of double pass solar air collector without porous absorbing material and single pass collector respectively.

Comparison of heating and natural ventilation in a solar house induced by two roof solar collectors

In this paper, two kinds of roof solar collectors (RSCs), namely, the single pass RSC, and the double pass RSC are analyzed and compared. The double pass roof solar collector, which is configured by integrating a double pass solar air collector with the building roof, can be operated more efficiently for space heating in winter, and for natural ventilation in other seasons. To evaluate the effects of two RSCs for both space heating and natural ventilation, a single traditional Chinese style house, on which the two RSCs will be mounted respectively, is developed. Through comparison, it is found that the instantaneous efficiency of solar heat collecting for the double pass RSC is higher than that of the single pass one by 10% on average, and natural ventilation air mass flow rate contributed by natural ventilation for the double pass RSC can be improved to a great extent for most cases, indicating that double pass RSC is superior to the single pass one from the points of view of both space heating and natural ventilation. The double pass RSC is therefore more potential for improving indoor thermal environment and energy saving of buildings.