Experimental and Numerical Investigation of a Semispherical Solar Still, Chamber Stepwise Basin, with and without a PV Powered Electrical Heater

The world's need for drinkable water is increasing with a growing population. The desalination process using solar energy is the cheapest and most straightforward method that can be used to generate pure water from saline water by utilizing energy from the sun's free heat source. A semispherical and chamber stepwise basin solar still with an inclined glass cover, with and without PV powered electrical heaters as another power source can increase the rate of evaporation of saline water, thus increasing the productivity of semispherical solar still. In this investigation, a conventional solar still and semispherical solar still with and without PV-powered electrical heaters were invented and worked in parallel with the experimental setup to make a good comparison between these models. The experimental results show that stepped semispherical with PV-powered electrical heater and without PV-powered electrical heater solar stills enhanced the productivity of freshwater from a conventional solar still by 156.6% and 72.5%, respectively. The theoretically simulated model is obtained using Mathcad software, and is compared with experimental results. Semispherical solar still productivity increases with increased solar intensity and with a PV-powered electrical heater as an additional power source. The theoretical results concluded from the mathematical model are in good agreement with experimental results.

Increasing the Flow Capacity of Hoses with Electrical-Heater Coils to Supply Thickened Preservatives for Spraying

Introduction. Anticorrosion protection of agricultural machinery working elements is provided through using pneumatic application of thickened preservatives with heating. For this purpose, a wire coil is inserted inside the preservative-supply hose and connected to a current source. It is known that the wire thickness and the coil pitch affect the hydraulic resistance to fluid flow. However, it has not been established how the diameter of the coil insert and its heating affect the flow capacity of the flexible hose channel. The purpose of the research is to increase the capacity of a flexible hose with an electrical-heater coil. For this purpose, it is necessary to determine its geometric parameters minimizing the hydraulic resistance to the thickened preservative flow and reducing the energy consumption for heating the material in the hose. Materials and Methods. It is proposed to investigate two electrical-heater coils of the same length, but of different diameter, made of steel welding wire pieces of equal length. There was developed a stand to study the influence of the inserted coil parameters on the hose hydraulic resistance. The stand was used to determine pressure losses in hoses with coils and in smooth hoses when used engine oil and thickened preservative flow through them. The flow capacity of the hose with cold and heated coils was estimated. Results. The method of heating the preservative in the hose wall layer is justified. At the same time, its flow capacity increases one and a half times with less energy consumption (2.4 times) than when heating the preservative in the central part of the hose. Under laminar flow mode, the pressure loss in the hose is 2 times lower when the coil is equal to 0.85 of the hose channel diameter than when the coil is equal to 0.67 of the channel diameter. Discussion and Conclusion. The research found the rational way of placing the electrical coil near the heated hose channel wall. At low air temperature, the reduction of the thickened preservative viscosity by heating in the hose helps to decrease the pressure loss up to 50% and increase its flow capacity by 1.4‒2.0 times. The use of a electrical-heater coil in the hose with thickened preservative will minimize energy consumption when preserving equipment on open storage sites.

Experimental analysis of the thermal comfort provided by an electrical heater and a heat pump

After considering heating sector, one realises that there is no clear and consensual way to quantify or qualify the thermal comfort of the different technologies available to satisfy the heating demand of a home. This contribution tries to call attention to this by means of an experimental study of the thermal comfort provided by two very different technologies, an electrical heater and a heat pump. To do so, a test matrix is developed by considering [2]. Some experiments are carried out in a climate chamber constructed following [1]. The variables registered are used to determine the comfort variables defined in [3] for each technology. After both technologies are compared and some conclusions are drawn.

Recent advances in solar drying system: A Review

Research on solar dryer technology proliferates since it reduces the drying period while keeping nutritional values in the agricultural products. This paper presented a review of recent advances in the solar drying system. This review is composed of working principles and classifications of solar dryers. They were classified into two main elements: airflow modes, either passive or active, and the way heat is transferred: direct, indirect, mixed-mode, and hybrid. The hybrid system used several types of elements to supply additional heat in the drying system, as elaborated in this paper, such as the electrical heater, biomass, and photovoltaic system. The advantages and disadvantages of the solar dryer also being discussed in this paper

Improvement of Heat Sink Performance Using Graphite and Graphene Coating

This experimental research depicts the role of coating hot surfaces by graphite and graphene on the process of heat dissipation from these hot surfaces. Three aluminum specimens have been prepared for test, one of theme is coated by graphite, another one by graphene a while the third is left free of coating for comparison purpose. Each specimen is tested separately in a home-made wind tunnel. A plate electrical heater is adhered on the bottom of the specimen to simulate the generated energy by a heat sink. A heat sink composed of high thermal conductivity was applied between the heater plate and the base plate of heat sink to reduce the contact resistance to heat flow. The experiments are conducted with four turbulent Reynolds number. The results reveal that the sample coated by graphene exhibits the best thermal dissipation while the uncoated specimen shows the worst thermal performance.

Performance study of a baffled solar dryer

<abstract> <p>This paper presents a hybrid solar dryer with baffles disposed of on the solar collector. When the levels of solar radiation are low, an electrical heater is used to increase the drying air temperature. A photovoltaic system feeds the electrical heater and the fans, and it is also used to preheat the drying air, increasing the temperature at the inlet of the solar collector. Experimental results of corn drying indicated that the baffles augmented the energy efficiency of the system (from 23.5 to 24.9%) and the temperature rise in the solar collector (from 13.5 to 20.2 ℃), reducing the time required for the corn to reach the final desired moisture content.</p> </abstract>

In-Situ Measurement of Electrical-Heating-Induced Magnetic Field for an Atomic Magnetometer

Electrical heating elements, which are widely used to heat the vapor cell of ultrasensitive atomic magnetometers, inevitably produce a magnetic field interference. In this paper, we propose a novel measurement method of the amplitude of electrical-heating-induced magnetic field for an atomic magnetometer. In contrast to conventional methods, this method can be implemented in the atomic magnetometer itself without the need for extra magnetometers. It can distinguish between different sources of magnetic fields sensed by the atomic magnetometer, and measure the three-axis components of the magnetic field generated by the electrical heater and the temperature sensor. The experimental results demonstrate that the measurement uncertainty of the heater’s magnetic field is less than 0.2 nT along the x-axis, 1.0 nT along the y-axis, and 0.4 nT along the z-axis. The measurement uncertainty of the temperature sensor’s magnetic field is less than 0.02 nT along all three axes. This method has the advantage of measuring the in-situ magnetic field, so it is especially suitable for miniaturized and chip-scale atomic magnetometers, where the cell is extremely small and in close proximity to the heater and the temperature sensor.