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 enhancement of a CO2 heat pump system recovering stack exhaust thermal energy in fuel cell vehicles
Abstract A CO2 heat pump system using recovered heat from the stack coolant was provided for use in fuel cell vehicles, where the high temperature heat source like in internal combustion engine vehicles is not available. The refrigerant loop consists of an electric drive compressor, a cabin heater, an outdoor evaporator, an internal heat exchanger, an expansion valve and an accumulator. The performance characteristics of the heat pump system were investigated and analyzed by experiments. The results of heating experiments were discussed for the purpose of the development and efficiency improvement of a CO2 heat pump system, when recovering stack exhaust heat in fuel cell vehicles. A heater core using stack coolant was placed upstream of a cabin heater to preheat incoming air to the cabin heater. The performance of the heat pump system with heater core was compared with that of the conventional heating system with heater core and that of the heat pump system without heater core, and the heat pump system with heater core showed the best performance of the selected heating systems. Furthermore, the coolant to air heat pump system with heater core showed a significantly better performance than the air to air heat pump system with heater core.
Experimental study on ground vibration of blasting the boulder with tandem shaped charging warhead
Hazardous effects of blasting the boulder with the new breaking-blasting equipment-tandem shaped charging warhead are mainly air shock wave, seismic wave and blast slung shot. Blast-induced ground vibration is one of the inevitable effects and may cause substantial damage to nearby structures. Started from the formation process and mechanism of ground vibration to study the seismic wave, the research attained curve of vibration velocity of monitoring points by TC-4850 and carried out differential and fast Fourier transform analysis of the curve. And the results concluded that blasting vibration with tandem shaped charging warhead mainly comes from prime charge; the attenuation law can be predicted by Sadev’s Formula. Explosion vibration frequency range is 20-150 Hz, while with the increase of distance from the blasting center, blasting vibration intensity attenuates rapidly, vibration duration increases and vibration frequency gradually reduces. Compared with general rock blasting, its attenuation rate of blasting vibration is faster with higher frequency and smaller impact on buildings, but the harm effects should not be ignored for the special application environment.