Influence Of Coolant Research Articles

Study on 3D Simulation Performance of Large‐Scale Proton Exchange Membrane Fuel Cell with Distribution Region

The majority of the current research examines fuel cell performance metrics using single channels or small‐area flow fields, but fails to take into consideration the actual shape of the flow field of modern proton exchange membrane fuel cell (PEMFC). The homogeneous distribution of reaction gas concentration and liquid water distribution is examined using 3D computational fluid dynamics simulation on a commercial large‐scale PEMFC with 113.92 cm2 reaction area and distribution region as the object. The results show that the gas distribution in the fluid flow is effectively optimized under the action of the distribution zone, and the maximum concentration error of anode is 4.87%, which is far less than that of cathode, and the higher the flow rate in the flow channel, the stronger the water removal ability; the effects of different working pressure and flow direction of reactant gas on gas concentration in catalytic layer and water content in proton exchange membrane are also studied. The results show that higher working pressure is beneficial to improve the performance of fuel cell, and countercurrent mode is better; finally, the influence of coolant is analyzed, and the results show that coolant can effectively reduce the internal temperature of the fuel cell, which is beneficial to improve the life of the fuel cell.

Influence of coolant and material properties on cooling high-temperature steel spheres in subcooled ethanol-water mixtures

The paper presents the new experimental results on cooling high-temperature steel spheres in subcooled ethanol-water mixtures at mass fractions of ethanol in the range of 10–80% under atmospheric pressure. Three test samples of 39 mm in diameter each have been prepared for the experiments: a carbon steel sphere with the oxidized surface and two stainless steel spheres. In the latter samples, one sphere had a polished surface, while the other one had a carbon coating. Usage of binary liquid mixtures as cooling liquids allows changing their thermophysical properties in a wide range. In general, when decreasing ethanol mass fraction boiling heat transfer intensifies, and it leads to an earlier (at higher surface temperature) transition to the intensive heat transfer regime. The experimental results are qualitatively consistent with a model that was proposed by authors earlier. This model describes the conditions of transition from a stable film boiling to an intensive heat transfer regime (so-called “microbubble boiling”). The main idea of the model is that this regime can arise due to the local contacts between the crests of the wavy liquid flow at the liquid/vapor interface and the protrusions of the surface roughness. The model considers the properties of a coolant (latent heat of evaporation, surface tension and kinematic viscosity) and thermophysical properties of a cooled surface (thermal effusivity). The experimentally obtained values of heat transfer coefficients in stable film boiling regimes are in agreement with the calculation results of the semi-empirical model of heat transfer in stable film boiling of subcooled liquids developed by authors earlier.

Analysis of output characteristics introduced by non-uniform coolant in direct-liquid-cooled multi-disk laser

Abstract The near field of the probe beam after passing through the gain module is measured. The “streamer effect” is first discovered in the experiment, which is characterized as continuity in the flow direction and non-uniformity in the lateral direction with high spatial frequency. To explain the “streamer effect”, a fluid–solid coupling model and an unstable resonator oscillation model of the direct-liquid-cooled thin-disk laser are established. The simulation results show that the non-uniformity of the coolant along the width of the flow channel gives rise to the streamer effect. A feasible cooling channel to achieve a high uniformity coolant is proposed and experimentally verified. At CW pumping of 9.6 kW, the influence of coolant on the output beam quality can be controlled at β

Physical mechanism of ultrasonic machining

In this paper, the main aspects of ultrasonic machining of constructional materials are considered. Influence of coolant on surface parameters is studied. Results of experiments on ultrasonic lathe cutting with application of tangential vibrations and with use of coolant are considered.

Numerical Modeling of Regenerative Cooling System for Large Expansion Ratio Rocket Engines

In this study, the performance of regenerative cooling system for large expansion ratio rocket engines (Ae/At ∼ 100) is investigated numerically. During combustion and gas expansion, the walls of the combustion chamber and the rocket nozzle are exposed to high temperature gas (∼3500 K), which can ultimately lead to structural failure. Therefore, to protect the hardware from thermal failure, a regenerative cooling system for a cryogenic rocket engine that uses fuel (liquid hydrogen (LH)) or oxidizer (liquid oxygen (LOX)) as the cooling medium is considered. Three-dimensional simulations have been performed for both constant and variable fluid properties. The influence of the thermal properties of the material and thickness of the nozzle wall on conductive heat transfer has also been investigated. The effect of radiative heat transfer when there is no regenerative cooling system has been analyzed. In addition, heat transfer enhancement for different turbulence models and the influence of coolant used (both the fuel and oxidizer) is also investigated. It is evident from the results that a properly designed regenerative cooling system can maintain the hot side wall at a temperature well below the melting point of the wall material, which ensures the protection of nozzle hardware from thermal failure. Also, the predicted pressure drop is found to be 0.7 bar, which meets the design requirement. Numerical predictions are validated with the data available in literature.

Research on Recycling Technology of Vanadium Extracting Waste

Based on the features of vanadium extracting waste in PanGang, technology ideas are proposed as following: vanadium extracting waste ash is used as coolant in converter, vanadium extracting and vanadium extracting residue is used as slagging material in steelmaking. Influence of slagging material on oxidability of molten steel in converter is analyzed, such as iron and steel consumption, effect of dephosphorization, influence of coolant on semisteel quality after extracting vanadium, and quality of vanadium slag. New way to utilize the waste is developed. Recycling the vanadium extracting waste in PanGang, mitigate the environmental pressure.

Influence of Coolant in Machinability of Titanium Alloy (Ti-6Al-4V)

Application of titanium alloy has increased many fields since the past 50 years. The major drawback encountered during machining was difficult to cut and the formation of BUE (Built up Edge). This paper presents the tool wear study of TTI 15 ceramic insert (80% Aluminum oxide and 20 % Titanium carbide) on machining Ti-6Al-4V at moderate speed with and without the application of water soluble servo cut S coolant. Titanium alloy is highly refractory metal and machining titanium is challenging to the manufacturers. Experiments were carried out on medium duty lathe. Application of coolant tends to reduce toolwear and minimize adhesion of the work material on the cutting tool during machining and also improves the surface finish. Result provides some useful information.

Influence of coolant on the performance of internal combustion engines

The influence of coolant properties on the performance of internal combustion engines is investigated, and means of coolant improvement are considered.

Tribological aspects of machining aluminium metal matrix composites

In this paper, tool wear, surface integrity and chip formation are studied under both dry and wet cutting conditions. The turning results showed that the influence of coolant on tool life was more pronounced at higher cutting speeds than at lower cutting speeds. This is mainly because of the dominance of the mechanical wear mechanisms at lower cutting speeds and the lack of formation of a lubricating layer/film that can reduce the friction between the abrasive particle and the cutting tool. When turning at higher speeds, under wet conditions, the tool life was increased. However, the surface quality was deteriorated. This was mainly due to the flushing away of the partially debonded particulates from the machined surface, thus, forming higher percentage of pit holes and voids. The formation of chips with serrated edge was more pronounced during wet cutting, as a result of high thermal gradient. The microhardness measurements on the aluminium matrix beneath the machined layer showed higher values when cutting under wet conditions.

High-Performance Surface Grinding – The Influence of Coolant on the Abrasive Process

The availability of newly designed grinding machines with high stiffness. high spindle power and wheel speeds, super-abrasive CBN-grinding wheels, adaptive dressing techniques, coolant delivery, coolant filter, and wheel surface cleaning systems enables application of the high-performance grinding method. This grinding technique using CBN-grinding wheels, can be characterized by high cutting speeds, relatively high material removal rates, and good surface finish. This paper presents the consideration of chip thickness and its influence on the grinding process, due to the grinding parameters, such as cutting speed, depth of cut and work speed. Results obtained in practical investigations concerning the impact of the coolant delivery, on the emerged forces and on the power demand at high peripheral wheel speeds are discussed.