Papers by Keyword: Active Cooling

Abstract: This work aims to develop safety shoes, with thermal regulation systems, namely innovative heating and cooling systems. Heating system was developed using printing techniques; and cooling system was developed using the integration of Peltier modules in the shoe structure. These materials are based on the Peltier effect, in which, when an electric current is applied, the heat moves from one face to the other, being subsequently removed using thermal dissipation methods. This effect allows an active cooling. Given the high technological challenge of integrating cooling systems into footwear, this paper will present only developments related to cooling system.

Abstract: In hypersonic environments, the development of aircraft engine presents the mitigation of the extreme thermal environment inside the combustion chamber. This paper establishes the capabilities for combustor panel design. By given the key loading and boundary conditions of the panel structure, the thermal structural analysis determines temperatures and stresses and the optimization improves panel’s robustness subject to thermal mechanical loads. A parametric sweep analysis is carried and the results give the optimal value of the panel face thickness.

Abstract: Heat transfer characteristics of China RP-3 kerosene under supercritical state were experimentally investigated. Results showed that at sub-critical pressures, heat transfer deterioration happens, and the wall temperature rises from approximately 350°C to 750°C. This is thought to be resulted from film boiling when kerosene begins to transfer from liquid to gas. At supercritical pressures, heat transfer enhancement was observed. And it is mainly caused by the sharp increase of specific heat of kerosene when the wall temperature is approaching the critical temperature of kerosene. The heat transfer coefficient doesnt increase with velocity for kerosene, because the thermal properties and residence time of kerosene have changed when velocity is changed.

Abstract: Coking characteristics of China RP-3 under high temperature (above 650°C) and long-duration (20 minutes) conditions, especially the effects of temperature, pressure, and inner diameter of cooling channels on coking amount were experimentally investigated. Temperature of kerosene in experiments varied from 650°C to 730°C, pressure varied from 1.8MPa to 3.5MPa, and the mass flow rate was approximately 120g/min. Results showed that temperature has a significant influence on coking amount. Even a small increment of temperature induces remarkable coke formation. However, pressure and inner diameter of the tube has a relatively little effect on it. The coking amount increases as pressure and inner diameter increase, but the increasing rate is decreasing. It is considered that inner diameter mainly affects residence time. When residence time increases to some extent, coking amount begins to grow slowly even stop increasing. This is resulted from two reasons. Firstly, the cracking conversion percentage reaches an upper limit when residence time is adequately long; secondly, coke gradually covers the inner wall of the tube, leading to isolation of kerosene from the metal surface to form coking.

Abstract: Experimental investigations were made on the instability of supercritical kerosene flowing in active cooling channels. Two approaches were used to control the pressure in the channel. One is the back-pressure valve while the other is the venturi. In both conditions, a kind of low-frequency oscillation of pressure and temperature is observed. And the oscillation periods are calculated. By comparison with the flow time, it is concluded that the instability occurred in active cooling channels is probably one kind of density wave instability. And its period has no relationship with the cooling channel geometry, nor the pressure, but only depends on the flow time of kerosene in active cooling channels. When the mass flow rate, density and pressure drop couple with each other, the density wave instability will appear.

Abstract: Large caliber naval gun weapon system in sustained and rapid firing process, produced high temperature and high pressure gas will form pulsed high temperature flow in barrel, causing the barrel being heated and cooled sharply and then being in bad environment, affecting the life of the barrel. The research object of this paper is based on 155mm naval gun, to utilize the theories of fluid mechanics and heat transfer and use ANSYS-CFX software, to simulate the heat response of the gun’s rifling original portion under interlayer active cooling, and to analyse the effects of structure parameters of interlayer cooling system and flowing parameters of cooling liquid on cooling performance using the principle of heat transfer enhancement, providing guidance for the optimization of the structure of the interlayer cooling system.

Abstract: To allow better machining heat transfer through mist evaporation, a new active cooling method is proposed. It is based on variable strength activation of coolant together with active cooling. A key issue in the proposed method is the use of multiple actuators of high frequency vibration for extra strength increase. This will rely on the idea of focusing and superposition. In this project, experimental tests were conducted to test the idea for the proposed variable strength activation of coolant in precision machining. Experimental test results show that the effects of ejection distance de on the vibration sensor output amplitude Aa and output frequency fa are not significant. The output amplitude Aa has a linear relationship with the number of actuator na. The effects of na on fa is not obvious. Based on the results, the idea of using multiple actuators for focusing and constructive superposition in variable strength activation is confirmed.

Abstract: A new active cooling method is proposed for increased cooling effectiveness of coolant in grinding. It is based on variable strength activation of coolant together with active cooling to allow better machining heat transfer through mist evaporation. Multiple actuators are used through superposition and focusing. A device of variable strength coolant activation has been developed. Preliminary experimental tests were conducted to test the feasibility of the proposed cooling method. It is found that, using the proposed variable strength activation, an improvement of 87.6% in Ra value and 71.9% in Rq value were obtained when compared with the existing activated and cooled coolant cooling method.

Abstract: In order to enhance the cooling performance, better understanding of the effects of coolant parameters is necessary. In this project, a total of five input parameters for actively cooled and activated cutting fluid were studied. An aerosol spectrometer was used to measure the particle size spatial distribution of the cooling mist in the fluid. Taguchi method was used in the design of experiments. It was found that the unit volume net specific particle counts exhibit the behavior of oscillation and attenuation of a second order dynamic system. Cooling mist particle spatial frequency ranges from 0.01269/μm to 2.5/μm, the weighted average size ranges from 0.3051μm to 3.714μm and the particle size difference for 99.8% count attenuation ranges from 0.5μm to 19.7μm. The order of importance of the input parameters was studied and the coolant concentration was found as the most important input parameter for the unit volume net particle counts.

Abstract: An actively cooled and activated cooling approach is proposed and examined in this project in order to deal with the problems associated with methods such as the cryogenic cooling method. It is also aimed to further improve the surface quality of the workpiece after grinding by combining the advantages of the existing cooling methods. Both computational and experimental studies were conducted for grinding the brittle materials with the proposed approach. Optical examinations were used to study the surface morphology. The experimental results show that the surface quality can be improved by up to 23.75% on average in terms of surface roughness Ra. The computational test reveals that the heat can be taken away more effectively by the proposed approach.