GB1147025A - Phytotron - Google Patents

Abstract

1,147,025. Air-conditioned chambers. A. SHAW. 19 April, 1966 [20 April, 1965], No. 17139/66. Heading F4V. [Also in Divisions A1 and G3] In a system controlling the atmosphere in a chamber 100 for growing plants and having a refrigeration system, heating, and also humidifying means control means are provided responsive only to changes in true loads (e.g. heat transfer through the chamber walls, from lights and due to the transpiration of the plants) and the total load on the refrigeration system is substantially constant. The control means comprises a dry bulb temperature sensor 123 and a humidity sensor 122, a reheater 131 and a dew-point control 135. A day and night clock programmer 141 is fitted. The apparatus comprises an insulated chamber 101 containing the plants, the controlled atmosphere entering a plenum chamber 108 and passing through a perforated diffuser 109 to registers 124 through which the atmosphere passes to an air conditioning unit 127. This unit includes an expansion coil 129 of a refrigeration system 126, a filter 137, a preheater 128 (which prevents frosting), a reheater 131, a fan 134 and a humidifying pan and heater 135, 136 respectively. A light chamber 102 ventilated by a fan 103 and drawing air through a filter 104 is provided. Some fresh air may be admitted at 142 and excess air is spilled out at 143. If the humidity ratio becomes excessive the system operates on a 100% recirculation basis and a metered supply of carbon dioxide replaces the air admitted by inlet 142. In a modification, the humidity ratio setting is controlled independent of the dry bulb temperature settings and this is achieved by introducing low pressure steam by a modulating steam valve or by a modulating pan humidifier. A fine, manual, overriding control is provided. The apparatus may be used for testing a refrigeration expansion coil under varying conditions in which case the coil to be tested replaces the coil 129 and the "chamber" becomes an insulated duct in the region of the inlet to the coil. In this embodiment, the preheater and fresh air and overspill vents are not required.