Journal of Heat Recovery Systems最新文献

The possibility of using thermocouples made from BiTe alloys in thermoelectric generation is investigated. A prototype has been assembled at the ‘Istituto di Fisica Tecnica’ in Palermo University using thermoelectric modules commercially available and normallu used for thermoelectric refrigerators. Some experimental results are summarized; the hot source temperature during the test runs lies in the range 30–110° and ascertained efficiency is up to 2%.

Adsorption heat pumps have sparked considerable attention in recent years. In this paper general outlines for adsorption heat pumps are presented and the results of the work related to an adsorption heat pump which has been built and tested are given. The hermetically sealed heat pump system mainly consists of a packed bed of adsorbent, a condenser and an evaporator. A natural zeolite and water vapour pair is used as the working material. Heat of adsorption and heat of condensation are utilized for heating and heat of evaporation is utilized for cooling purposes.

A moderator heat recovery scheme is proposed for CANDU reactors. The proposed circuit utilizes all the moderator heat to the first stages of the plant feedwater heating system. CANDU-600 reactors are considered with moderator heat load varying from 120 to 160 MW_th, and moderator outlet temperature (from calandria) varying from 80 to 100°C. The steam saved from the turbine extraction system was found to produce an additional electric power ranging from 5 to 11 MW. This additional power represents a 0.7–1.7% increase in the plant electric output power and a 0.2–0.7% increase in the plant thermal efficiency. The outstanding features and advantages of the proposed scheme are presented.

The suitability of working fluids for use in high temperature heat pump systems has been considered on the basis of their volumetric and other thremodynamic properties. The change of thermodynamic properties with temperature has been graphically illustrated. It is shwon that water becomes increasingly attractive as a working fluid as the delivery temperature approaches 200°C. A heat pump using water as the fluid is capable of an actual coefficient of performance of five and a gross temperature lift of 70°C for a condensation temperature of 200°C.

This paper presents the qualitative feasibility of two waste heat recovery concepts for geothermal refrigeration and airconditioning. The high temperature available at shallow depths of abandoned or dry wells in oil fields and the natural gas which is being flared without any use near oil producing wells, can be used as heat input for vapour absorption cooling systems. Depending upon the quantity and quality of low grade heat from these sources, conventional refrigerant-absorbent combinations, e.g. water-lithium bromide and ammonia-water may be used for refrigeration and airconditioning purposes in the Basic vapour absorption systems.

This project at Clayton Aniline Co. (CAC) demonstrates the use of a finned-tube heat exchanger and run-around coil system to recovery heat from a spray-dryer exhaust to pre-heat the inlet air. It was originally envisaged that this would reduce the energy consumption of the dryer by 12%, equivalent to 9.4 therms/h.

Funding was granted by the Energy Efficiency Office of the Department of Energy under the Energy Efficiency Demonstration Scheme for the installation and monitoring of the project. This project is one of a package of demonstrations for heat recovery in spray dryers. A parallel project at ABM Chemicals uses a glass tube heat exchanger to recover energy from the dryer exhaust, and a further project at BIP Chemicals demonstrates the use of a separate heat source to pre-heat the dryer inlet air.

Within the U.K., widespread adoption of heat recovery on spray dryers would lead to energy savings of 2,500 TJ/yr or 100,000 tonnes of coal equivalent (tce)/yr. It is estimated that, within the next 5 yr, around 20% of this will be achieved, resulting in savings of around 20,000 tce/yr, worth £1.6 million yr.

The heat recovery system was installed at CAC in July 1982. Unfortunately, due to the built-up of solids on the fins, the unit had to be removed after only three days operation. The equipment was therefore modified and the changes included:

reducing the number of fins from from 8/in. to 4/in.: this reduction in are meand a 30% loss of potential savings;

improving the exchanger spray wash system by including an additional row of nozzles directed towards the centre of the unit.

The replacement exchanger was installed in July 1984 and, since that time, has operated satisfactoryly. It has not adversely affected the operation of the spray dryer, as the problems of excessive solids deposition and ineffective washing have now been overcome.

Detailed monitoring has not yet been completed, but preliminary information and design calculations estimate that for the modified exchanger, energy savings averaging 6.5 therms/h (191 kW) are probable. These are worth about £17,200 to CAC and hence the payback period on the installation cost of £35,200 is 2 yr.