An introduction to heat transfer

Leu-M

Data Reduction And Error Analysis For The Physical Sciences

New heat conversion technologies need to be developed and improved to take advantage of the necessary increase in the supply of renewable energy. The Organic Rankine Cycle is well suited for these applications, mainly because of its ability to recover low-grade heat and the possibility to be implemented in decentralized lower-capacity power plants. In this paper, an overview of the different ORC applications is presented. A market review is proposed including cost figures for several commercial ORC modules and manufacturers. An in-depth analysis of the technical challenges related to the technology, such as working fluid selection and expansion machine issues is then reported. Technological constraints and optimization methods are extensively described and discussed. Finally, the current trends in research and development for the next generation of Organic Rankine Cycles are presented.

Techno-economic survey of Organic Rankine Cycle (ORC) systems

An organic Rankine cycle (ORC) machine is similar to a conventional steam cycle energy conversion system, but uses an organic fluid such as refrigerants and hydrocarbons instead of water. In recent years, research was intensified on this device as it is being progressively adopted as premier technology to convert low-temperature heat resources into power. Available heat resources are: solar energy, geothermal energy, biomass products, surface seawater, and waste heat from various thermal processes. This paper presents existing applications and analyzes their maturity. Binary geothermal and binary biomass CHP are already mature. Provided the interest to recover waste heat rejected by thermal devices and industrial processes continue to grow, and favorable legislative conditions are adopted, waste heat recovery organic Rankine cycle systems in the near future will experience a rapid growth. Solar modular power plants are being intensely investigated at smaller scale for cogeneration applications in buildings but larger plants are also expected in tropical or Sahel regions with constant and low solar radiation intensity. OTEC power plants operating mainly on offshore installations at very low temperature have been advertised as total resource systems and interest on this technology is growing in large isolated islands.

Low­grade heat conversion into power using organic Rankine cycles - A review of various applications

The organic Rankine cycle (ORC) is commonly accepted as a viable technology to convert low temperature heat into electricity. Furthermore, ORCs are designed for unmanned operation with little maintenance. Because of these excellent characteristics, several ORC waste heat recovery plants are already in operation. Although the basic ORC is gradually adopted into industry, the need of increased cost-effectiveness persists. Therefore, a next logical step is the development of new ORC architectures. Even though there has been a strong renaissance towards ORC research in the last decade, ORC architectures have received relatively little attention. Several barriers can be listed. First, there is the difficulty in assessing the additional complexity of the system. While several advanced cycle designs appear promising from a thermodynamic viewpoint, it is not clear that these represent viable economic solutions. Secondly, there is a lack of experimental data from open literature. Additionally, there is the challenge of coping with various boundary conditions from literature, which makes an objective comparison difficult. In this article an overview is presented of ORC architectures. The performance evaluation criteria and boundary conditions are clearly stated. As well, an overview of the available experimental data is given.

Review of organic Rankine cycle (ORC) architectures for waste heat recovery

Micro-CHP systems for residential applications

Earth-air heat exchangers, also called ground tube heat exchangers, are an interesting technique to reduce energy consumption in a building. They can cool or heat the ventilation air, using cold or heat accumulated in the soil. Several papers have been published in which a design method is described. Most of them are based on a discretisation of the one-dimensional heat transfer problem in the tube. Three-dimensional complex models, solving conduction and moisture transport in the soil are also found. These methods are of high complexity and often not ready for use by designers. In this paper, a one-dimensional analytical method is used to analyse the influence of the design parameters of the heat exchanger on the thermo-hydraulic performance. A relation is derived for the specific pressure drop, linking thermal effectiveness with pressure drop of the air inside the tube. The relation is used to formulate a design method which can be used to determine the characteristic dimensions of the earth-air heat exchanger in such a way that optimal thermal effectiveness is reached with acceptable pressure loss. The choice of the characteristic dimensions, becomes thus independent of the soil and climatological conditions. This allows designers to choose the earth-air heat exchanger configuration with the best performance.

Thermohydraulic design of earth-air heat exchangers

Thermodynamic analysis of energy storage with a liquid air Rankine cycle

The growth of renewable energy requires flexible, low-cost and efficient electrical storage to balance the mismatch between energy supply and demand. The Carnot battery buffers electrical energy by storing thermal energy (charging cycle mode) from a resistive heater or a heat pump system when the electricity production is higher than the demand. When electricity demand is higher than the production, the Carnot battery generates power from the stored thermal energy (power cycle mode). This paper is a review of this emerging and innovative technology, including a market analysis. First, the different possible technologies and configurations of Carnot batteries are described. This includes charging cycles, power cycles and thermal energy storage systems. Furthermore, a state-of-the-art of the existing prototypes in the world is given. The performance indicators for this technology are unclear, and this paper tries to define objective performance indicators. Finally, all the described technologies are compared, and conclusions are drawn to help engineers select the optimal technology for a given case.

Michel De Paepe

Papers

Review of organic Rankine cycle (ORC) architectures for waste heat recovery

Micro-CHP systems for residential applications

Thermohydraulic design of earth-air heat exchangers

Thermodynamic analysis of energy storage with a liquid air Rankine cycle

Carnot battery technology: A state-of-the-art review