Abstract. The paper presents heat transfer research basing on a long fin with a circular cross-section. Its basis is welded to the pipe where the hot liquid paraffin, having a temperature of 70oC at the inflow, is pumped. The analyzed element is a recurrent part of a refrigeration's condenser, which is immersed in a paraffin. The temperature of the inflowing liquid is higher than the temperature of the melting process for paraffin, which allows the paraffin to liquify. The temperature at the basis of the rib changes and it is assumed that the heat transfer is quasi-stationary. On this basis the estimation of the mean value of heat transfer coefficient was conducted. The unsteady thermal field of the investigated system was registered with an infrared camera V50 produced by a Polish company Vigo System. This device is equipped with a microbolometric detector with 384 × 288 elements and the single pixel size 25 × 25 ȝm. Their thermal resolution is lower than 70 mK at a temperature of 30 o C. The camera operates at 7,5 ÷ 14 μm long-wave infrared radiation range. For a typical lens 35 mm the special resolution is 0.7 mrad. The result of the calculations is mean heat transfer coefficient for the considered time series. It is equal to 50 W m -2 K -1 and 47 W m -2 K -1 on the left and right side of the fin, respectively. The distance between the experimental data and the curve approximating the temperature distribution was assessed with the standard deviation, Sd = 0.04 K.
Abstract. The paper presents the measurement of heat transfer coefficient for the refrigerator's condenser in free convection regime. The water was pumped through the steel coils of heat exchanger with a constant flow rate and its temperature was kept at a demanded value by means of ultrathermostat. The research was conducted in stationary conditions which were controlled by a continuous measurement of the water temperature at inflow and outflow to the heat exchanger. The temperature distribution at the external condenser surface was registered by means of an infrared camera. Single elements used to the analysis were selected using the thermogram registered. In free convection regime and in case of small temperature change the heat transfer coefficient value can be calculated by comparing the measured temperature area with analytical solution describing one-dimensional temperature distribution along the rib. The accuracy of the proposed method for measuring the heat transfer coefficient was examined by comparing the heat transferred to the air and the heat lost by water flowing through the spiral of heat exchanger. An error between these two parameters is about 6%.
Hybrid installations with respect to renewable energy sources are becoming more popular due to the stringent requirements for the energy efficiency of buildings. Therefore, the thermomodernization of a district-heating substation was proposed. Several scenarios, including different renewable energies (an air–water heat pump versus a heat pump with photovoltaics), different investment financing (equity or bank credit), and different purposes for heating demand (central heating or central heating with ventilation and domestic hot water), were analyzed. The economic aspects involved the calculations of the payback time and net present value, while the ecological and environmental characteristics were weighed using emission reduction. Each of the analyses resulted in different proposed modernization methods. However, taking both factors together, the computations proved that the most profitable was the scenario with energy demand for heating, domestic hot water, and ventilation purposes financed by means of bank credit with a thermomodernization bonus.
Thermography is getting more and more popular in many fields of everyday life nowadays. It is successfully applied in heat investigations. Infrared cameras imaging includes thermal analyses of building physics, thermal bridges or insulation improvement inspection. Flir E30 infrared camera was used in order to conduct measurements of two chimneys located in Kielce Power Station in Poland. The first tested facility is a structural steel chimney thermally isolated with mineral wool. The other chimney is built of reinforced concrete material. An infrared camera tests enabled the creation of the diagrams presenting the temperature distribution along the chimneys in different orientations. The research proved the correct functioning of both chimneys.
Thermal building inspections indicate the growing interest among researchers due to the global climate changes resulting in legislations and policy contribution to low-energy consumption. The technologies applied during the experiments involve infrared cameras: both hand-held and on unmanned aerial vehicles. The research conducted in the public building in Kielce included the analysis of glass partition from the inside of the building by means of hand-held and UAV camera. The temperature distributions presented in the graphs proved that both methods are accurate in case of such investigations. However, during the experiments, it was concluded that hand-held camera is far more convenient.
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