Low-level Heat Source Research Articles

Solar Thermal Collector System with Parabolic Collector for Applications in Organic Rankine Cycle: Design, Manufacturing and Testing

Generating power using an Organic Rankine Cycle (ORC) has the advantage of converting waste energy into useful power. This technology can utilize various low-level heat sources such as biomass, engine waste heat, geothermal and solar, and it significantly reduces thermal pollution as well as the reliance on fossil fuels. In this research, a parabolic collector with a tube length of 18.12 meters was designed and manufactured. The results showed that the parabolic trough can reach a temperature of 56.6℃ with a water flow rate of 0.042kg/s, from an initial temperature of 28.2℃ during a 2-hour test. The average turbine output power was 430.04 W in theoretical calculations and 248.57 W in reality for the ORC system. The highest thermal efficiency was achieved at a turbine inlet temperature of 63.5℃ and a turbine inlet pressure of 10.5 bar, with a value of 4.489%. Overall, using ORC technology can effectively utilize low-level heat sources and contribute to reducing reliance on fossil fuels and thermal pollution.

ファンコイルユニットにおける低レベル熱源利用特性に関する研究 : 第7報-熱源を含めたファンコイル空調システムの省エネルギー性の基本的評価

ファンコイルユニットにおける低レベル熱源利用特性に関する研究 : 第7報-熱源を含めたファンコイル空調システムの省エネルギー性の基本的評価

ファンコイルユニットにおける低レベル熱源利用特性に関する研究 : 第1報-二次元的模型による検討

ファンコイルユニットにおける低レベル熱源利用特性に関する研究 : 第1報-二次元的模型による検討

Absorption heat transformers – A comprehensive review

In recent years, the use of absorption heat transformers (AHTs) has reached a remarkable edge. AHTs have great potential in the utilization and upgrading of low-level heat sources. These are typically waste heat obtained from industrial processes and those supplied from solar and geothermal sources. Other benefits of absorption cycles include using significantly less electricity, potentially having less CO 2 emission, causing no ozone layer depletion, and using natural refrigerants; and these contribute to increasing the attractiveness of these machines. The use of absorption heat transformers has become even more popular as the cost of fossil fuel continues to rise. In the present work, a comprehensive literature review has been carried out on AHTs, their applications, crystallization risk, working fluids, as well as performance evaluation by applying different models and economic aspects.

Traçabilité des expositions professionnelles aux produits chimiques grâce à une base de données

Absorption heat transformers (AHTs) have great potential in utilization of low-level heat sources, such as industrial waste heat. However, the operation of an AHT is limited by heat sources, customer load, and cooling water. However, such conditions may change in practical applications. Thus, research on the off-design performance of an AHT is important and necessary. In this paper, mathematical models for the cycle and components of a vertical falling film AHT operating with water/lithium bromide solution were developed. The coefficient of performance, output heat capacity, and exergy efficiency were used to evaluate the performance of the AHT. Furthermore, the exergy loss distribution diagrams under off-design conditions were carried out, and the exergy loss ratio was decomposed into several factors to determine why exergy loss ratio varies under off-design conditions. Finally, exergy loss ratio in the solution heat exchanger plays an important role under off-design conditions, which is analyzed thoroughly. A kind of effective adjustment is studied and proven to be effective in improving the performance of the AHT. The present work provides a tool for thoroughly understanding the mechanism of performance change in the AHT under off-design conditions.

Energy and exergy analyses on the off-design performance of an absorption heat transformer

Absorption heat transformers (AHTs) have great potential in utilization of low-level heat sources, such as industrial waste heat. However, the operation of an AHT is limited by heat sources, customer load, and cooling water. However, such conditions may change in practical applications. Thus, research on the off-design performance of an AHT is important and necessary. In this paper, mathematical models for the cycle and components of a vertical falling film AHT operating with water/lithium bromide solution were developed. The coefficient of performance, output heat capacity, and exergy efficiency were used to evaluate the performance of the AHT. Furthermore, the exergy loss distribution diagrams under off-design conditions were carried out, and the exergy loss ratio was decomposed into several factors to determine why exergy loss ratio varies under off-design conditions. Finally, exergy loss ratio in the solution heat exchanger plays an important role under off-design conditions, which is analyzed thoroughly. A kind of effective adjustment is studied and proven to be effective in improving the performance of the AHT. The present work provides a tool for thoroughly understanding the mechanism of performance change in the AHT under off-design conditions.

On the effect of distributed cooling in natural ventilation

We examine the natural ventilation flows which develop when a low-level heat source interacts with a distributed zone of cooling at high level in an enclosed space. We develop some new analogue laboratory experiments in which we use a saline plume to model a localized heat source and a heated plate to model a distributed source of cooling. The experiments show that in a building with a low-level point source of heating, a two-layer steady stratification develops in which the depth of the lower layer decreases as the intensity of the cooling at the ceiling increases. We develop a theoretical model which accounts for the penetrative entrainment across the interface associated with the convection in the upper layer. We show that this becomes more dominant as the cooling increases and eventually the room becomes well-mixed. We discuss the role of such distributed cooling on the design of natural ventilation and its ability to provide sufficient flow and adequate temperature control.

Development of Evaporation Equipment for Reforming by Spray Flow.

An experimental study was conducted in order to establish the thermal and fluid design criteria for a new steam reforming device, and a proposal was submitted to employ a flow laden with droplets (water and methanol mixture solution) directly impinging on a heated plate in the new reforming device. Experiments have been conducted by controlling spray impingement on a heated plate covered with a porous plate made by sintered metal. The new configuration of the reforming device is able to enhance the evaporation of liquid by using a low-level heat source held at lower than 600K. Droplets atomized by a spray nozzle instantaneously evaporate on the heating surface without bouncing, since the sintered metal surface provides a higher Leidenfrost temperature due to surface roughness. The characteristics of spray flow and evaporation efficiency have been measured by Phase Doppler Anemometer which permits local measurements of size and velocity of liquid droplets, size distribution and mass flux of droplet. Results have confirmed that superheated gas was directly generated from the spray liquid with high efficiency, and the locations of heating plates and spray nozzle were optimized. Finally the rate of evaporation was enhanced by pre-heating the liquid before atomization.

A Study on Characteristics of Fancoil Unit Utilizing Low Level Heat Sources : Part 6-Fundamental Study for Optimum Combination of Supply Air Flow Rate and Width of Air Outlet in FCU System

A Study on Characteristics of Fancoil Unit Utilizing Low Level Heat Sources : Part 6-Fundamental Study for Optimum Combination of Supply Air Flow Rate and Width of Air Outlet in FCU System

Studies on the Characteristics of Absorption Refrigerator Driven by Two Different Heat Sources. 1st Report, Hot Water and Steam.

In this report, we investigate the characteristics of an absorption refrigerator driven by two different heat sources, hot water and steam, to make use of waste heat from fuel cell. This type of refrigerator consists of the cyclic combination of the single-effect absorption refrigerator and the double-effect one. For absorption refrigerators, there are many types of cycles which depend on solution circulation and generator combinations. First, the optimum cycle from the viewpoint of recovering waste heat is clarified. Then the simulation model is constructed and the static characteristics are investigated. Furthermore, the effects of low-level heat source on the total COP is clarified. There is a lower limit of temperature of the low-level heat source because the temperature becomes lower than solution temperature. Furthermore, we discuss the temperature control when low-level heat source conditions vary and the flow rate of steam is varied.

Study on Characteristics of Fancoil Unit Utilizing Low Level Heat Sources : Part 5-Fundamental Study for Starting Characteristics of FCU System Using Unsteady State Numerical Calculation

Study on Characteristics of Fancoil Unit Utilizing Low Level Heat Sources : Part 5-Fundamental Study for Starting Characteristics of FCU System Using Unsteady State Numerical Calculation

Study on Characteristics of Fancoil Unit Utilizing Low Level Heat Sources : Part 3-Fundamental Study Using Numerical Calculation for Residential Room

Study on Characteristics of Fancoil Unit Utilizing Low Level Heat Sources : Part 3-Fundamental Study Using Numerical Calculation for Residential Room

堆肥発酵熱回収操作の物質，エネルギー，エクセルギー収支 １ 堆肥材料内の微視的収支式の誘導

Composting heat generator is a low level heat source compared with those using combustion of fuels such as petroleum and LNG. Because it is low level in temperature, composting heat generator will not be applied to heat recovery system unless it is designed to restrict energy loss and exergy dissipation as little as possible. Exergy is known to be useful to evaluate the availability of every kind of energy not only from its quantity but also from its quality.For optimization of a target heat recovery system from composting heat generator, mass, energy and exergy balances must be predicted properly under any possible operating condition. Because there is a temperature difference between the heat generator and medium fluid in a heat exchanger inserted in the generator, temperature does not become uniform in the generator. In order to predict the amount of energy and exergy recovered from such heat generators of non-uniform temperature in detail, the balance equations must be treated microscopically.In the present paper, microscopic balance equations of mass, energy and exergy in the composting heat generator are derived systematically, following a transport phenomena model with chemical reaction for porous or dispersed media. Then, the balance equations are simplified to equations of practically available form, because the mass flux by diffusion can be neglected compared with that by convection under the usual aerating condition of composting.The amount of heat and exergy possible to be recovered will be theoretically predicted by solving the balance equations derived here with suitable boundary and initial conditions introduced for the target heat recovery system.

A Study on Characteristics of Fancoil Unit Utilizing Low Level Heat Sources : Part 2-A Experimental Research for Real Size Room

A Study on Characteristics of Fancoil Unit Utilizing Low Level Heat Sources : Part 2-A Experimental Research for Real Size Room

Unified description of endoreversible cycles.

A more general model of endoreversible cycles is constructed on the basis of the models of endoreversible three-heat-source cycles and generalized Carnot cycles. Its optimal configuration and fundamental optimum formula are studied. It is pointed out that the optimum formula may be used to discuss the effect of finite heat source and thermal resistance on the performances of various thermodynamic cycles. Some more significant results than those of classical thermodynamics can be obtained. They may provide some new theoretical bases for the exploitation and application of the new technology of three-heat-source cycles applying low-level heat sources such as solar energy, geothermal energy, waste heat, and so on. Simultaneously, it is also expounded that many important conclusions in the current literature concerned with endoreversible cycles may all be included in the optimum formula. It is thus clear that the formula can make a unified description of various endoreversible cycles discussed in finite-time thermodynamics. Obviously, the major significance of such a description lies in that it can promote the development of finite-time thermodynamics and the establishment of a systematic theory.

Heat transport cycle with methyl alcohol-acetaldehyde chemical reaction

The exothermic reaction of acetaldehyde and methyl alcohol is suggested as a candidate for energy transport and upgrading. A temperature rise of up to 50°C could be obtained for this system. A lower heat source could also be upgraded by using two distillation columns working at different pressures; thus a low level heat source at 60°C could be delivered to a consumer centre at 70°C by this method.

Nitric acid cycle process for extracting thermal energy from low-level heat sources

A process for recovering thermal energy from a low-level heat source has been devised. The process utilises the heat generated when nitric acid and water are mixed. The temperature rise in a single-effect unit is about 20 °C, but a higher temperature is attained in a multiple-effect unit.