Beräkningsmodell för oljekylare

Sammanfattning: In this thesis, a calculation model for oil coolers has been worked on for Ursviken Technology AB press brakes Optima and Optiflex. Analysis of the theory behind physical phenomena has shown that a series of factors in a hydraulic system give rise to heat increase of hydraulic oil. To keep the service life, efficiency, and quality of oil as high as possible, cooling is needed.  A difficulty in calculating the cooling demand in a press brake is how much the temperature increases in the oil during operation. A simpler test of how much the temperature increases during a defined operating time and press cycle program has been conducted and it exhibited a linear temperature increase over time. The test was carried out with and without a drive (Eco pump) that allows the main motor to run only when press cycles are performed and thus not during idling. The tests gave an indication of how much heat rose at each press cycle. The difference between Eco pump on and turned off was very small. This is believed to be because the press program used never allowed the impact of the main engine and thus more tests are recommended to detect difference in temperature rise during the given time.  Coolers are dimensioned based on the amount of heat in the oil that needs to be cooled and is the cooling power P required by the cooling machine. It is calculated using:     is the temperature change in the oil below  ,   is the heat capacity the oil has,   is the density of the oil and   is the volume of the oil. The equation for P gives an amount of heat in kW that can be compared to the cooling capacity and flow of coolers from manufacturers' data sheets. One difficulty is to obtain one   during a given time where tests of press brakes may be needed for better calculation.    The most important parameter for determining whether a compressor cooler or fan oil cooler is best suited is the ambient air temperature. The best cooling effect of a fan oil cooler is obtained if the ambient air is as cool as possible, which gives greater temperature difference to the hot oil. If the ambient air temperature is close to the required oil temperature, the cooling capacity will be lower, and a compressor cooler will perform better in that environment. A disadvantage of fan oil coolers is noise from the fan and in those environments where the noise level is important, a compressor cooler should be chosen instead. A fan oil cooler has a low purchase price (compressor coolers are up to five times more expensive) and the fan oil cooler's energy consumption is so small that it has no major economic effect. High heat supply is conditions that give rise to wear on a hydraulic oil and therefore the highest temperature the oil is exposed to is important to limit. Increased heat in the hydraulic oil leads to reduced viscosity and this causes the shear resistance to decrease. The press brakes work indoors, which makes it easier to regulate the temperature compared to outdoor applications. The recommended operating temperature range is 30°C-60°C but the temperature sensitivity to lower temperatures has been difficult to verify in theory. In this study, the service life and durability of the oil has mainly been studied and not how engine components are affected by the temperature of the oil.