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Two-phase thermal energy conversion system

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A two-phase thermal energy conversion system employs an evaporable liquid such as water, and a gas which is not liquefiable within the operating temperature and pressure ranges, such as air. The water and air are mixed and one of the two or both are heated so that the water evaporates and is absorbed by the air to result in a pressure increase. The increase of pressure or volume can be converted into mechanical energy by a prime mover such as a turbine or reciprocating piston engine. The heat of condensation is utilized and converted into mechanical power while the temperature and pressure are reduced. The liquid, such as water, may be below its boiling point. If the water consists of salt water, fresh water is derived as a condensation product from the prime mover.

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A bi-directional two-phase/two-phase heat exchanger

August 1993

This paper describes the design and test of a heat exchanger that transfers heat from one two-phase thermal loop to another with very small drops in temperature and pressure. The heat exchanger condenses the vapor in one loop while evaporating the liquid in the other without mixing of the condensing and evaporating fluids. The heat exchanger is bidirectional in that it can transfer heat in ... [Show full abstract] reverse, condensing on the normally evaporating side and vice versa. It is fully compatible with capillary pumped loops and mechanically pumped loops. Test results verified that performance of the heat exchanger met the design requirements. It demonstrated a heat transfer rate of 6800 watts in the normal mode of operation and 1000 watts in the reverse mode with temperature drops of less than 5 C between two thermal loops.

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March 2003 · International Journal of Energy Research

Performance test results of new alternative refrigerant mixtures such as R-410A, R-507, R-407C, and R-404A under various conditions of magnetic field are discussed, analysed and presented. The test results were obtained using an air-source heat pump set-up with enhanced surface tubing under various magnetic field conditions. Performance tests were conducted according to the ARI/ASHRAE ... [Show full abstract] Standards. The test results demonstrated that as magnetic field force increases, compressor head pressure and discharge temperature slightly increase as well as less liquid refrigerant is boiling in the compressor shell. This has a positive effect in protecting the compressor. The effect of magnetic field on mixture behaviour varies from one mixture to another depending upon the mixture's composition and its boiling point. Furthermore, the use of magnetic field appears to have a positive influence on the system COP as well as thermal capacities of condenser and evaporator. Copyright

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The Condensation and Evaporation of Liquid Droplets in a Pure Vapour at Arbitrary Knudsen Number

July 1991 · International Journal of Heat and Mass Transfer

J.B. Young

A new set of equations describing the growth and evaporation of small liquid droplets in a pure vapour are presented. The equations, which model both mass and heat transfer between the droplet and the vapour, are in simple closed form solution and are suitable for practical calculations at any Knudsen number. The physical model on which the theory is based is essentially that of Langmuir but some ... [Show full abstract] novel features are incorporated. For example, the velocity distribution function for molecules approaching the liquid surface is described by a simplified Grad, thirteen-moment distribution. The results of the analysis are in close agreement with other, more complicated and less general theories to be found in the literature. In particular, the temperature jump across the Knudsen layer in the continuum limit is accurately predicted. It is also shown that Maxwell moment methods based on the Lees, two-stream Maxwellian distribution lead to incorrect results.

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Occurrence of temperature spikes at a wetting front during spontaneous imbibition

December 2017 · Scientific Reports

It is reported that temperature rises at wetting front during water infiltration into soil. The temperature goes back to the background value after passage of water front. Different explanations have been provided for source of energy causing temperature spike. Some have contributed it to heat of condensation released due to condensation of vapor on “dry” solid surface. Some other stated that the ... [Show full abstract] heat of wetting or heat of adsorption is responsible for the temperature rise. In this research, we revisited this issue. First, we provide a comprehensive review about occurrence of temperature spike at a wetting front. Then, we report about experiments we performed on the rise of water in dry paper. Using infrared and optical imaging techniques, we could monitor temperature changes in time and space. For all samples maximum temperature rise occurred at the wetting front. The magnitude of temperature spike depended on paper material, thickness, and liquid composition. It was larger for cellulose-fiber-based paper than for plastic-based paper. For a given paper type, thicker samples showed a larger temperature spike. Adding salt to the water caused reduction of temperature spike. It was concluded that replacement of air-solid interface with water-solid interface releases energy, which causes temperature rise.

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The Maximum Experimental Safe Gap for a Spray of Higher Flash Point Liquid

April 1988 · Journal of Hazardous Materials

Brian Capp

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January 1970

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The effect of phase change on stability of convective flow in a layer of volatile liquid driven by a...

April 2017 · Journal of Fluid Mechanics

Buoyancy-thermocapillary convection in a layer of volatile liquid driven by a horizontal temperature gradient has been studied extensively in experiment and numerics. Recent studies have shown that the composition of the gas phase, which is typically a mixture of vapour and air, has a noticeable effect on the critical Marangoni number describing the onset of convection as well as on the observed ... [Show full abstract] convection pattern. Specifically, as the total pressure or, equivalently, the average concentration of air is decreased, the threshold of the instability leading to the emergence of convective rolls is found to increase rather significantly. We present a linear stability analysis of the problem which shows that this trend can be readily understood by considering the transport of heat and vapour through the gas phase. In particular, we show that transport in the gas phase has a noticeable effect even at atmospheric conditions, when phase change is greatly suppressed.

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The Role of Interfaces in Heat Transfer Processes

January 1983 · Advances in Colloid and Interface Science

Jer Ru Maa

An understanding of the role of interfaces between phases is essential to true understanding of many heat transfer processes. In the cases of evaporation ion and condensation in single component systems, the evaporation or condensation coefficient represents the transmitance of the vapor-liquid interface itself or the maximal possible rate of interfacial heat as well as mass transfer. Jet ... [Show full abstract] tensimetry is a simple but powerful technique for the study of the resistance of the interface in the evaporation and condensation processes, with or without chemical reaction, involving the interface between phases. This technique also eliminates most of the complications of the bulk phases on both sides of the interface. Get tensimetry and other recent experimental data verify that the evaporation coeffecients of water and other common liquids are unity or nearly unity; the interface does not constitute a significant resistance to the heat transfer processes.

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Experimental investigations of arterial thermal tubes

May 1992

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Numerical investigation of blade tip cavitation on large discharge condition of diagonal turbine

March 2019 · IOP Conference Series Earth and Environmental Science

A series of numerical simulations was carried out to estimate the cavitation characteristics for a diagonal flow turbine. The interaction between the tip leakage flow and the cavitation bubbles was investigated using the obtained numerical data. The evaporation and condensation process for cavitation phenomenon was described by using a simplified Rayleigh-Plesset equation. A two-phase homogeneous ... [Show full abstract] model was adopted to calculate the mixture of gas and liquid phases. Three types of cavitation with different origins were obtained around the blade tip region. The incipient cavitation was well-known tip clearance cavitation. In the present study, the occurrence of tip clearance cavitation was limited in the position where the clearance between blade tip and discharge ring spread, irrespective of Thoma number. Tip clearance cavitation was found out not to contribute to the decrease of the turbine efficiency. On the contrary, the turbine efficiency increased with the growth of tip clearance cavitation. When Thoma number decreased, the other type cavitation arose on the discharge ring surface. The development of the discharge ring cavitation led to the decrease of the turbine efficiency. In addition, so-called tip vortex cavitation obtained in the lower Thoma number condition than the appearance of discharge ring cavitation. These three types of cavitation were also observed in the experimental approach. The correlation between the decrease of the turbine efficiency and the development of discharge ring cavitation was also verified in the model test.

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Bottoming Gas Turbine-Electric Plant by Immiscible Liquid Cycle

October 1980 · Journal of Engineering for Power

B. M. Burnside

The use of the immiscible liquid binary cycle (ILBC) to recover exhaust heat from electric utility gas turbine plant is described. In simple dual pressure plant without L.P. turbine admission, increase in specific work output compared with the steam cycle and its variation with condenser pressure, turbine efficiency and exhaust gas temperature is presented. The penalty of larger condenser ... [Show full abstract] surfaces is quantified. A dual pressure steam—ILBC cycle with L.P. turbine admission, which should improve on the corresponding steam cycle, is proposed.

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Accurate Prediction of the Condensed Phase (Solid or Liquid) Heat of Formation of Triazolium-based E...

September 2018 · Central European Journal of Energetic Materials

A novel method is introduced for the reliable prediction of the condensed phase (solid or liquid) heat of formation (Δf H θ (c)) of triazolium-based energetic ionic salts (EISs) at 298.15 K. It is based on the influence of some specific elemental compositions of cations and anions as additive parts. Two correcting functions, as non-additive quantities, are also used to adjust the first part. The ... [Show full abstract] coefficients of the specific elemental compositions of cations and anions in the new correlation, with a negative sign as well as a negative correcting function in the triazolium-based EISs, can decrease the value of Δf H θ (c) for the corresponding EISs. The reported Δf H θ (c) values of 57 different triazolium-based EISs were used to derive the new model. For 34 triazolium-based EISs, where the outputs of quantum mechanical methods were available, the Root Mean Squared Error (RMSE) of the new model was 156.0 kJ/mol. Meanwhile, the RMSE of complicated quantum mechanical methods is very large, i.e. 298.0 kJ/mol. The high reliability of the new model was also confirmed for a further 5 complex triazolium-based EISs as compared to the results of quantum mechanical calculations.