The temperature of a PV (photovoltaic) panel increases when it produces electricity but its electrical efficiency decreases when the temperature increases. In addition, the electrical efficiency of the PV panel is very limited. To increase the PV efficiency, the rest of the solar irradiance must be used, together with the temperature being kept at an optimum value. With this purpose, an experimental study was conducted. Firstly, two specific photovoltaic-thermal (PV/T) systems were designed. The first was the PV/T system which used only a water heat exchanger. The other one was the PV/T system that used a water and air heat exchanger. In the latter PV/T system, air passed through both the top of the PV panel and the bottom of it while water passed through only the bottom of the panel in a separate heat exchanger. In this way, the water and air absorbed the thermal energy of the panel by means of separate heat exchangers, simultaneously. In addition to the two systems mentioned above, an uncooled photovoltaic module was also designed in order to compare the systems. As a result, three different modules were designed. This study was conducted in a natural ambient environment and on days which had different climatic conditions. The thermal, electrical and overall efficiencies of each PV/T module were determined. The results were compared with the uncooled module electrical efficiency. The results showed that when water and air were used together, it was more efficient than single usage in a PV/T system. The thermal gain of the working fluids was also found to be fairly high and so, the gained energy could be used for different purposes. For example, hot air could be used in drying systems and air condition systems. Hot water could be used in hot water supply systems.

Permeability and porosity of woolen fabrics are investigated experimentally in this paper. Permeability experiments are conducted in a wind tunnel to the TS 391-EN ISO 9237 standard. Woolen fabric is placed in the test section of the wind tunnel to measure permeability to airproofing . Velocity measurements are made used a hot wire anemometer in the front and rear of the wool. Air permeability is closely related to pore size and distribution. So, it is important to study porosity, in order to classify and determine the right use of woolen fabrics. Many methods are used to estimate porosity. In this study, the theoretical model is used for determination of porosity values, and the influence on porosity of various fabric parameters was investigated. Depending on the permeability, weft and warp density, weight, fabric thickness and porosity relationship are investigated. The results are presented as graphs.

Steam ejectors are one of the key components of steam ejector refrigeration/heat pump systems. Steam ejector is required to compress low-pressure stream to a higher pressure. Steam ejectors have no moving part, a simple structure, low cost, reliability, easy installation, high vacuum performance, corrosion resistance, and no consumption of electrical energy. In this study, steam ejector design was modeled using finite volume techniques, and Mach number and pressure in constant cross-section have been compared with analytical data reported in the literature. In this work, numerical calculations were performed with ANSYS Fluent(ANSYS FLUENT Theory Guide, ANSYS, Inc. Release 17.2, 2016, Canonsburg, PA, USA), a computational fluid dynamic code. In the turbulent flow, heat transfer-based analyses were performed using energy equations.

Nozzles are widely used to control the rate of flow, speed, direction, mass, shape and pressure of the stream in connection with many different engineering applications. This paper presents the performance predicted by a computational fluid dynamic (CFD) model, which are 3D models that utilize parametric analysis, realizable k-epsilon turbulence models and experimental measurement for a jet. Jet flows are ejected from three different slot nozzles: round-shaped nozzle, rectangular-shaped nozzle and 2D-contoured nozzle. In this numerical study, velocities of free jets have been predicted for different axial distances from the nozzle exit in the range of $0.2\le z/B\le 12$ when center velocity at the nozzle exit. CFD simulation results are compared to experimental results from literature. These results are consistent with the existing experiments.