Doug Probert

Influence of the domestic hot-water daily draw-off profile on the performance of a hot-water store

An enhanced TRNSYS simulation model, NEM, of the behaviour of a domestic hot-water (DHW) store, with an immersed heat-exchanger (HX), has been developed and validated. This model simulates the dynamic heat-depletion and recovery processes in the immersed HX and predicts the transient temperature-patterns for various DHW draw-off versus time profiles. Realistic daily profiles (RDPs), based on field studies, were developed to provide representative draw-off patterns for the testing of thermal stores and simulation studies. The effects of these RDPs and five other existing profiles on the stores performance are analysed using the enhanced model. The simulation results indicate the importance of the HXs recovery, as well as the number, type and time of occurrence of the draw-offs in the profile, on the thermal stores performance. It is concluded that RDP profiles should be used in the performance testing of thermal stores to obtain results that reflect conditions experienced in the field.

Wind-energy harnessing: Global, national and local considerations

A review of the global issues of wind-energy capture and use is given, along with a case for developing the wind-energy potential of part of the Rhymney Valley, South Wales. Such an energy-supply project should be incorporated into an integrated energy and environmental strategy for the region. This would not only yield benefits with respect to the local, national and global environments, but also aid in enhancing the quality of life for the Rhymney Valley region and its inhabitants.

Thermodynamic behaviour of an air-conditioning system employing combined evaporative-water and air coolers

The performance of an open absorption-system, energized by low-grade heat such as insolation and/or waste heat, has been investigated. This combined evaporative cooler (CEC) [i.e. an indirect evaporative cooler (IEC) together with a direct evaporative-cooler (DEC)] was used to cool the air. A computer simulation of the cooling cycle was devised, so that the performance characteristics of the system could be predicted for a range of operating conditions: the influences of various design-parameters on the coefficient of performance (COP) were also evaluated. The COP of the CEC system was at least 20% greater than those achieved when employing either the IEC or DEC systems alone.

Heat transfers and radial flows via a viscous fluid squeezed between two parallel disks

For the physical system (shown in Fig. 1 in the paper), the convective effect in the axial direction is considered and an analytical solution of the governing equations achieved. Good agreement is found between the analytical and numerical solutions so corroborating the approach adopted. For a small gap between the disks, heat actually flows into the upper disk, even though the imposed temperature difference would initially have been considered to cause the heat flux to be out of the upper disk. The radial pressure-distribution in the viscous liquid is presented as a function of the Reynolds number and R0/d ratio. Axial bulk convection rises as the separation between the two disks increases. Fig. 1. (a) Schematic section orthogonal to the two identical parallel disks; approach velocity u; (b) three-dimensional view of the two identical parallel disks.

Environmental impacts of air traffic

Environmental degradation caused by emissions from aircraft is likely to increase in severity with the growth of flying. Until recently, such emissions were considered to be insignificant, but during the last five years, this view has been reversed. The complexity of the effects of pollution in the atmosphere has now been realised, at least qualitatively. The known consequences of some of the main emissions are discussed along with current environmental legislation and pertinent UK Government policy with regard to aviation. Recommendations are given for some future UK transportation-by-aircraft policy objectives that would safeguard the future of our, as yet, relatively pollution-free skies.

‘Mundic’-type problems: a building material catastrophe

Abstract During the period ad 1900–1950, readily-available mining spoils, specifically mundic and killas rocks, were used as aggregates in concrete in order to keep building costs low. Unfortunately this choice of materials, especially in Cornwall and Devon, had led subsequently to the occurrence of many structural faults. Consequently the affected buildings have experienced significant losses in financial value and some have even had to be demolished because they were unsafe. The deleterious process in the concrete ensues as a reaction with water: thus one of the primary means to try to reduce its severity is to maintain the concrete in a dry condition.

Integrated approach for the achievement of environmental sustainability

The evolvement and implementation of a sustainable environmental strategy (which conforms with global initiatives such as Local Agenda 21) is demanding and complex, both for local and national governments. It requires simultaneously the practices of energy thrift and hence environmental protection. Therefore, it is desirable to simplify the activities involved into a simple, easy-to-follow procedure. This is attempted in this report.