Design of an apparatus with controlled rates of temperature change for use in cold tolerance tests of conifers

Graduation date: 1969An apparatus was designed to permit freezing tests of\ud needles and other tissue parts from coniferous trees under\ud controlled rates of temperature change with time. The design\ud is based on the principle of a balanced system of refrigeration\ud demand and heat input to achieve a steady temperature state.\ud The apparatus permits the operator to decrease temperatures\ud from 0°C to -40°C at rates of 1, 2, 3, or 4°C per hour, to hold\ud temperatures at the desired freezing level from 1 to 24 hours,\ud and to increase to 0°C at rates of 1, 2, 3, or 4°C per hour.\ud Temperatures achieved within the sample tubes are accurate\ud to within ± 0. 9°C of the expected temperature