Performance Characteristics of PTC Elements for an Electric Vehicle Heating System
A high-voltage positive temperature coefficient (PTC) heater has a simple structure and a swift response. Therefore, for cabin heating in electric vehicles (EVs), such heaters are used either on their own or with a heat pump system. In this study, the sintering process in the manufacturing of PTC elements for an EV heating system was improved to enhance surface uniformity. The electrode production process entailing thin-film sputtering deposition was applied to ensure the high heating performance of PTC elements and reduce the electrode thickness. The allowable voltage and surface heat temperature of the high-voltage PTC elements with thin-film electrodes were 800 V and 172 °C, respectively. The electrode layer thickness was uniform at approximately 3.8 μm or less, approximately 69% less electrode materials were required compared to that before process improvement. Furthermore, a heater for the EV heating system was manufactured using the developed high-voltage PTC elements to verify performance and reliability.
Heating Performance Characteristics of High-Voltage PTC Heater for an Electric Vehicle
High-voltage positive temperature coefficient (PTC) heaters have a high heating capacity and are fast acting; thus, they function as the actual main heating equipment in electric cars, and considerable research is devoted to improving their heating performance and efficiency. We evaluated the heating performance of a high-voltage PTC heater for an electric car by building a closed-loop-type test system including an air channel, environment chamber, DC power supply, and data acquisition system, and designed an initial prototype with general characteristics. Using this test system, we analyzed the heating performance characteristics of the heater as a function of changes in the blower airflow, ambient temperature, and battery voltage. We changed the geometrical variables of the heater and conducted an analysis to improve the heating performance and output density of the initial prototype. Based on the heating performance of the initial prototype and its geometrical variables, we designed an improved prototype and compared its heating performance and output density with that of the initial prototype. As a result, we achieved a heating capacity of 5.52 kW, a pressure drop of 48.2 Pa, and an efficiency of 98%, whereas the output density was 3.45 kW/kg, which is a 24% improvement over the initial prototype.
Exergetic analysis and evaluation of a new application of gas engine heat pumps (GEHPs) for food drying processes
In this study, three medicinal and aromatic plants (Foeniculum vulgare, Malva sylvestris L. and Thymus vulgaris) were dried in a pilot scale gas engine driven heat pump drier, which was designed, constructed and installed in Ege University, Izmir, Turkey. Drying experiments were performed at an air temperature of 45Â Â°C with an air velocity of 1Â m/s. In this work, the performance of the drier along with its main components is evaluated using exergy analysis method. The most important component for improving the system efficiency is found to be the gas engine, followed by the exhaust air heat exchanger for the drying system. An exergy loss and flow diagram (the so-called Grassmann diagram) of the whole drying system is also presented to give quantitative information regarding the proportion of the exergy input dissipated in the various system components, while the sustainability index values for the system components are calculated to indicate how sustainability is affected by changing the exergy efficiency of a process. Gas engine, expansion valve and drying ducts account for more than 60% amount of exergy in the system. The exergetic efficiency values are in the range of 77.68-79.21% for the heat pump unit, 39.26-43.24% for the gas engine driven heat pump unit, 81.29-81.56% for the drying chamber and 48.24-51.28% for the overall drying system.