Thermal accumulators

A preliminary procedure has been developed for assessing the prospective performance of idealised sensible- and latent-heat storage systems. Design charts relating storage volume, thermal capacity, boundary insulant thickness and time constant are presented.

Thermal insulation provided by dry, single-layer clothing materials

At 20 ± 2°C for a wide range of clothing fabrics, which usually have high air-volume voidages, the thermal resistance to [`]dry' heat transfers (apart from boundary layer contributions on their faces) is proportional to the fabric thickness. This resistance exhibits a maximum at a fabric density of approximately 90 kg m-3.

Thermal resistance behaviour of single and multiple layers of clothing fabrics under mechanical load

The thermal resistances of clothing assemblies comprising up to eight dry layers, in series, of a single fabric (either woven cotton, polyester or nylon) in air at atmospheric pressure have been measured and compared with other materials. Application of a compressive loading led typically to the resistance of a stack of eight polyester cloth layers falling from 46 x 10-3 Km2 W-1 under zero loading to 32 x 10-3 Km2 W-1 under 31 Nm-2. The percentage reduction in resistance for an additional equal increment of loading would be considerably smaller. Under load, the thermal behaviour of multiple layer assemblies is identical to that of a single layer of the same material and overall thickness and so it was concluded that contact resistances between successive layers are usually of secondary importance for clothing fabrics in air at atmospheric pressure and that the insulation provided by such an assembly is primarily dependent upon the volume of air held stagnant within the matrix, provided that no thermal radiation [`]windows' are present.

Reducing consumption by cascading energy inputs according to temperature level

The conventional first law energy balance accounts for all energy inputs to a system in terms of eventual energy rejection to the environment. The second law analysis examines the thermodynamic grade of energy presented to each station within the system. A simple model is analysed to demonstrate the energy savings possible by cascading energy flows according to second law principles.

Energy management

Metering, critically examining and if necessary modifying the energy flow through a system is desirable in order to achieve a high efficiency. Systematic procedures for energy management and audit of processes and products are suggested: they involve energy flow charts and assessment questionnaires and there by facilitate the location, and reduction or elimination, of energy profligate sub-systems. Design rules for the improvement of energy flow systems are listed.