Recent developments have prompted a review of evaporative cooling technology as an effective means of cooling modern deep plan buildings. Prominent among these developments is the success of high temperature sensible cooling systems, particularly, chilled ceilings, which require a supply of cooling water at 14-18 8C. Crucial to the success of evaporative cooling technology, as a significant means of cooling in modern applications, is the ability to generate cooling water, in an indirect circuit, at a temperature which closely approaches the ambient adiabatic saturation temperature (AST) or wet bulb temperature (WBT). Recent experimental research has demonstrated that it is technically viable to generate such cooling water at a temperature of 3 K above the ambient AST.While the frequency of ambient AST occurrence can be obtained from meteorological sources, there is little in-depth analysis of the potential for this form of cooling water generation, based on the approach temperatures which have now been shown to be viable. The decision to use an evaporative cooling system depends largely on an assessment, in-depth, of net energy saved against capital expended. Such an assessment requires detailed data on the availability of cooling water, generated by evaporation, for each location. This paper quantifies evaporative cooling availability in-depth for a northern and southern European city, Dublin and Milan and suggests a method of analysing such data for any world wide location, for which suitable meteorological records are available. The paper, incorporates recent experimental research findings and bases the availability analysis on meteorological test reference weather year data.The results of this research confirm a major potential for the generation of cooling water by evaporative means, which can be used to provide effective cooling of deep plan buildings by means of contemporary water based sensible cooling systems, such as fan coil systems, radiant chilled ceiling panels and ceiling cooling convectors (chilled beams). While the technique offers most potential in locations with a northern European temperate climate, it has significant potential to contribute to cooling in some southern European cities, during the nonsummer months and also at other times, particularly where load shaving techniques are incorporated. #

Meteorological enthalpy analysis of temperate and maritime climates above latitude 458N suggests that the water-side evaporative cooling technique has considerable unrealised potential with contemporary ''high temperature'' building cooling systems-such as chilled ceilings and displacement ventilation. As low approach conditions are the key to exploiting the cooling potential of the ambient air, thermal performance at such conditions needs to be investigated. To address the research issues, an industrial scale test rig, based on a low approach open cooling tower and plate heat exchanger and designed to maximise evaporative cooling potential, has been constructed.The thermal effectiveness of such systems (as a measure of the degree to which the system has succeeded in exploiting the cooling potential of the ambient air) is a key parameter. This paper presents the results of experimental research into the thermal effectiveness of a water-side, open, indirect evaporative cooling test rig, designed to achieve low (1-4 K) approach conditions in the temperate maritime climate of northern Europe. The sensitivity of the thermal effectiveness to a series of key operating variables is investigated. High thermal effectiveness of up to 0.76 was found with both cooling tower air-flow rate and secondary water-flow rate having a strong impact. Primary water-flow rate however, has a weak impact on thermal effectiveness but a major impact on energy performance-indicating scope for a considerable improvement in energy performance at the expense of a minor reduction in thermal effectiveness. A proposed energy efficient control strategy for this form of cooling water generation is proposed and supported by an analysis of the measured results. #

The success of chilled ceilings and displacement ventilation systems as a means of sensible cooling in buildings has prompted a review of evaporative cooling technology as an effective means of generating the required cooling water. When such cooling water is generated at low approach conditions (2-5 K), at the higher temperatures required in these systems (14-18°C), very high levels of availability result. In many north western European locations the levels of availability are such that the prospect of supplanting rather than simply supplementing the refrigeration system, for sensible cooling purposes, arises. The viability of the technique, however, largely depends on achieving low approach conditions, at acceptable levels of energy performance. Hence the need to investigate the energy performance of the process. This paper presents the results of recent experimental research into: i) the achievement of low approach conditions in an evaporative cooling test rig; and ii) the energy performance of this test rig when generating cooling water, indirectly, at the temperatures required for chilled ceilings. Energy performance is presented for a range of speci c conditions and typical annual ef ciencies of cooling water generation are determined. Results are compared with typical energy ef ciencies of conventional, vapour compression based, refrigeration systems. A signi cant potential for improved annual energy performance, is shown.

The experimental performance of an open industrial scale cooling tower, utilising small approach temperature differences (1-3 K), for rejection of heat at the low water temperatures (11-20°C) typical of chilled ceilings and other sensible air-water heat dissipation systems in buildings, is examined. The study was carried out under temperate maritime climatic conditions (3-18°C wet-bulb temperature range). Initially a theoretical analysis of the process at typical conditions for this climate was conducted, which indicated that a water to air (L/ G) mass flow rate ratio of less than 1.0 was required for effective operation. Consequently for these low L/G ratios, the thermal performance of the experimental tower was measured and correlated. A new correlation is proposed which shows a significant increase in the NTU level achieved, for the required L/G ratios (0.3-0.9). As the cooling tower in this application is predominantly a mass transfer device under summer conditions, the evaluation of the total volumetric heat and mass transfer coefficient (kg a s À1 m À3 ) is of particular relevance and is also determined.

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