The cooling apparatuses especially reffering to radiative cooling

Abstract

Some properties of frost action on a plant may be studied experimentally in the laboratory by means of the most easy way of cooling by conduction in contact with the freezing mixture. In this case however the temperature on the frost forming surface of the plant is higher than in the inside tissue of the plant when cooled down under the clear night sky. It is a matter of great difficulty to realize the noctual cooling passage taking place in the open field by introducing radiative cooling process in the closed chamber. The nuisance to get rid of arises from the frost formation on the outer wall of the cooling apparatus which prevents the cooling surface from frost deposition, our object really wished for.The 1st type of our apparatuses worked out consists of 2 concave aluminium mirrors facing each other at a little distance and the freezing mixture (or dry ice) and the surface to be frosted are put on each focus of the mirrors as shown in fig. 3, (or a hollow ellipsoid coated inside with gold is possibly better). The experimental test of this apparatus is not mostly satisfactory principally owing to the small scale apparatus as well as imperfectly refecting surfaces.The second type consists of 4 glass cylinders of different diameters as shown in fig. 4, CC cylinder being protected by means of thermally insulating wool cloth and humid or dry air flows into its enclose space through 4 small holes EE……and flows down through G, G. The middle part of the innermost cylinder is used as the cooling surface mape evident by the figure of a plant leaf. The cooling curves obtained by this cooling apparatus are shown in fig. 5 in which a fine lined cooling curve is due to the inflowing humid air and a quick temperature rise marked A arises from the sudden freezing of the supercooled drop of dew, and that marked B from that of the plant sap. The other thick lined curve is due to the inflowing dry air in which only one quick temprature rise B is noticeable there because owing to the sudden freezing of the supercooled plant and also owing to no formation of dew. Thus the 2nd type of our cooling apparatus meets demand most sufficiently and may be recommended to some worker in need of the frost investigation.