R.F. Babus'Haq

Forced steady-state convections from pin-fin arrays

The steady-state thermal and air-flow resistance performances of horizontally-based pin-fin assemblies have been investigated experimentally. The effects of varying the geometrical configurations of the pin-fins and the air-flow rates have been studied. The optimal pin-fin separation Sxopt in the span-wise direction, to achieve a maximum rate of heat transfer from the assembly, is 1·0 ± 0·2 mm

Feasibility of using an integrated small-scale CHP unit plus desiccant wheel in a leisure complex

By employing a natural-gas-fired combined heat-and-power (CHP) system in a leisure complex, the waste heat from the CHP units can be used to regenerate a desiccant wheel. The latter is employed to provide dehumidification for the indoor swimming pools in a leisure complex. A payback period of ~4 years has been predicted for this system, assuming zero amortised value for the CHP units that had to be replaced. Any resaleable value for the removed units would lead to an even shorter payback period.

Assessing the prospects and commercial viabilities of small-scale CHP schemes

Combined heat and power (CHP) is a technique which can provide both electricity and heat for industrial, commercial and/or residential buildings from a single source. Its implementation can make a significant contribution to reducing the fuel needs of the UK, offering as it does the prospects of overall energy-use efficiencies exceeding 80%. The present investigation deals with the application of small-scale CHP schemes to building services for providing winter heating and summer cooling; the latter being achieved using absorption heat-pumps. The assessments of the economic viabilities of such electricity-exporting schemes, and the predictions of the sizes of the total-energy plants necessary, involve tedious and prolonged numerical exercises. In order to be able to handle this type of problem in a routine and rapid manner, a comprehensive software package (available from the authors) has been compiled for use with a BBC desk-top computer. Building-services engineers can utilize this package to simulate theoretically the behaviours of CHP systems, in order to satisfy various scenarios concerning hourly energy-loading patterns for buildings for any day of the year, before having to make decisions as to whether or not to invest substantial amounts of money in installing a real plant.

The total energy approach: Evolution of combined heat and power for district heating and/or cooling

Combined heat and power (CHP) generation is not a new concept, but it provides an elegant solution to some of our present fuel problems, offering, as it does, 80% or greater efficiency. However, Great Britain lags behind other European countries with respect to the rate of introduction of CHP together with district heating and/or cooling (DHC) systems. Reviews of (i) the historical development of the designs of DHC pipelines, from insulated pipes in air-filled ducts to the modern preinsulated pipes buried in the ground, and (ii) sources of energy as well as developments in metering and control, for CHP-DHC systems, are presented. The cost effectiveness of each CHP-DHC system is highly sensitive to unit fuel prices, current discount rate, as well as the capital cost incurred. In the best interests of Britain, major governmental investments are now needed urgently in order to encourage the wider adoption of these systems.

Thermally insulating behaviour of single and multiple layers of textiles under wind assault

One or more layers of textiles can provide a thermal resistance between the human body and its environment, and so help maintain the body in a thermally comfortable state. The effect of wind on and its penetration through such thermal cladding is examined experimentally.

Economics of mini-combined heat and power packages for use in hotels

Abstract Combined heat and power (CHP) systems involve the simultaneous release of electrical (or mechanical) power and heat in the form of low-pressure steam or hot water. The assessment of the economic viabilities of mini-CHP packages and the predictions of their thermodynamic performances usually involve tedious and prolonged numerical exercises. Thus an existing software package has been modified and extended to handle this type of problem comprehensively, yet in a simple, routine and rapid manner. The pay-back period is estimated to be less than three years for the required mini-CHP package installation to satisfy the power and heating demands of each simulated two-storey hotel.

Natural convection across cavities: Design advice

Experimental measurements and theoretical predictions of steady-state heat transfers to or from horizontal single or double pipelines enclosed in horizontal circular or rectangular enclosures have been collated. The optimal configurations of the pipelines to achieve maximum thermal resistances of the air-filled cavities are identified. A recommended correlation for predicting the combined convective/conductive resistances provided by the contained air in a horizontal concentric annuli is presented.

Combined heat-and-power implementation in the UK: Past, present and prospective developments

The world is insufficiently concerned with ensuring its long-term energy supplies. For instance, a severe reduction of the availability of cheap fossil fuels is likely to occur in the mid twenty-first century. However, there are several steps that could be taken in the UK to ensure the sustainability of adequate power supplies (e.g. a Severn Barrage tidal-power harnessing system capable of satisfying ~8% of the electricity needs of the UK; a national campaign for the implementation, where economic, of combined heat-and-power (CHP) installations). The implementation of CHP technology is, even now, frequently an economically justifiable option which is capable of providing highly efficient, environmentally friendlier electricity and heat supplies. A variety of fuels, including oil, coal, natural gas, refuse, sewage, nuclear power and renewables, can be used as the energy source. Despite being thermodynamically attractive, the pace of adoption of CHP in the UK has been disappointingly slow. An historical record of the evolution of CHP as well as community (district) heating (DH) in the UK is presented. Recent developments and a possible future scenario for energy supplies, affecting the rate of adoption of CHP-DH systems in the UK, are outlined.

Steady State Heat Losses from Horizontal Pipes in an Air-Filled Rectangular Concrete Duct

Factors influencing the steady state heat loss behaviours of horizontal ‘supply’ and ‘return’ hot-water pipes, within an atmospheric pressure air-filled, relatively cold, horizontal rectangular trench, are considered. An experimental investigation concerning the effects of the displacement ratios for the two pipes revealed the optimal configuration, that is one which achieves a minimum steady state rate of heat loss from the supply pipe. For one set of temperatures for the pipes and trench walls, the optimal configuration of the supply and return pipes occurred at displacement ratios of +0.70 and −0.05, that is with the supply pipe in the upper region of the cavity and the return pipe vertically below it, the pipes being equidistant from the vertical walls of the trench. This configuration is of significance with respect to achieving maximum energy thrift for district heating pipelines, because it differs radically from the ‘side-by-side’ arrangement of pipes conventionally adopted in district heating practice.

Combined heat-and-power market-penetration in the UK: Problems and opportunities

Combined heat (and) power (CHP) technology is capable of providing efficient, environmentally-friendly, electricity and heat supplies. Despite being thermodynamically attractive, in the UK CHP has languished in the past and so failed to penetrate the market rapidly because of a lack of leadership by successive Governments. A frustrating chronicle for CHP as well as community (i.e. district) heating (DH) in the UK is presented. However, recent developments and a possible future scenario concerning energy supplies in the UK will change matters. It is predicted that the contribution of CHP will grow significantly as the UK energy supply business becomes increasingly customer-driven.