ISHS Acta Horticulturae 801: International Symposium on High Technology for Greenhouse System Management: Greensys2007
CHARACTERIZING OF COOLING EQUIPMENT FOR CLOSED GREENHOUSES |
| Authors: | H.F. de Zwart, F.L.K. Kempkes |
| Keywords: | Heat exchange, electricity consumption, energy requirement, climate management |
| Abstract:
The application of air conditioning devices for cooling greenhouses in summer is becoming increasingly popular in Dutch horticulture. Cooling reduces the ventilation requirement and, thereby, increases the benefits of carbon dioxide fertilisation. Moreover, when having enough cooling power, excessive temperatures can be prevented. Both improvements of the controllability of the greenhouse climate can enhance production in terms of quantity and quality. However, in commercial greenhouse industry, these benefits must more than balance the costs associated with the cooling equipment. An informed decision about the most apt equipment must rely on the computation of these costs. This is not a trivial issue because there are a lot of variables that determine the performance of an air conditioning unit. These variables comprise a combination of physical properties of the cooling devices, the greenhouse air conditions and the way of controlling the units. Since the specifications of air conditioning units are commonly available for only one, or only a small number of benchmark points, usually based on quite different applications from greenhouse horticulture, the department Greenhouse Horticulture of Wageningen UR has developed a software tool that translates arbitrary benchmark points to performance characteristics in a specified horticultural context. The tool relies on a mechanistic simulation model, based on solving heat and mass balances in a cross flow heat exchanger. This paper presents the design of this model, describes the relevant physics and shows some results. | |
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