Forced Air Heat Research Articles

Postharvest Quality of Early Season Grapefruit after Forced-air Vapor Heat Treatment

`Marsh' and `Ruby Red' grapefruit (Citrus paradisi Macf.) were harvested in Florida during Oct. and Nov. 1990, degreened in an ethylene chamber, exposed to vapor heat (VH) treatment (43.5 ± 0.1C for ≈240 min), and evaluated for deterioration in quality and development of injury after various storage regimes. Symptoms of aging averaged 6% and 8% of the surface on `Ruby Red' and `Marsh' fruit, respectively, and the VH treatment had reduced the incidence of aging by 45% after 5 weeks of storage (4 weeks at 16C plus 1 week at 21C). Total decay, mostly stem-end rots (Diplodia spp. and Phomopsis spp.), remained relatively low (≈5%) in both treated and nontreated fruit after 5 weeks of storage. The VH treatment had little effect on change in peel color during treatment or subsequent storage. After the final inspection, `Marsh' fruit was higher in total soluble solids and titratable acidity than `Ruby Red' fruit, but these quality indicators and pH were not affected by the VH treatment. VH treatment did not adversely affect the quality of `Marsh' or `Ruby Red' grapefruit harvested early in the season; hence, VH should be considered as a viable quarantine treatment for Florida grapefruit.

Forced air heat sink with new enhanced fins.

A forced-air-cooled heat sink with new enhanced fins was developed. The fin has many perforations and is bent to form a trapezoidal shape. The fin was enhanced in heat transfer by a breathing effect, a phenomenon by which the fluid is injected and sucked through the trapezoidal perforated fins. The thermal conductance of the heat sink at the same pumping power was about 1.6 times that of a similar heat sink with conventional plain fins, and also about 3 times at the same Reynolds number. A heat sink with the new enhanced fins designed for practical use was also shown.

Narrow Channel Forced Air Heat Sink

The heat transfer between the coolant anti the heat sink contributes a significant fraction of the thermal resistance of a package. It has been widely recognized that the heat transfer can be increased by increasing the area of the heat sink in contact with the coolant, and therefore the use of fins is common. However it has not been generally recognized that for laminar flow in confined channels, the heat transfer coefficient is inversely proportional to the width of the channel. Narrow channel forced air heat sinks have been designed, built, and tested. Three different channel widths, 5, 10, and 25 mils, were investigated. The design of the sinks permit integrated circuits (IC's) on 1/2 in centers and printed circuit (PC) boards on I in centers. The measured values of individual heat sinks with 30 I/min air flow are 5.5, 3.7, and 3.4°C/W for 25,10, and 5 mil channel widths, respectively. These values are in good agreement with calculated values. A 16 chip package with chips on 1/2 in centers was assembled utilizing 10 mil channel width heat sinks. A plenum fitted over the sinks supplied air to each of the sinks from a single source. The measured values of thermal resistance of the four center dies were between 5.3 and 5.9°C/W. If the chips are mounted directly on the sink instead of on the alumina substrate, the thermal resistance would be reduced by about 2°C/W.

Fireplace Performance

ABSTRACT FOURTEEN in-home tests were conducted on eleven different fireplaces to determine their overall perfor-mance including the heat loss during the cool down period. Ordinary fireplaces as typically operated were shown to be serious energy wasters. Outdoor air temperatures and wind appear to be two factors which greatly affect performance. Forced air heat exchangers and tightly fitting front enclosures can appreciably im-prove performance. However, the economic feasibility of fireplaces as heating systems is questionable even at the higher efficiencies provided by these accessories.

Regulation of core body temperature during whole body hyperthermia by oesophageal temperature feedback.

The use of whole-body hyperthermia as an adjuvant mode of therapy for metastatic cancer requires an accurate control of core body temperature so that the high temperatures encountered during treatment may be safely employed. Heating of the patient is accomplished by use of high-perfusion water-heated blankets. The temperature of the water circulating through the blankets is regulated by digital feedback control, using patient oesophageal temperature as a reference. A forced air heat exchanger is used to cool the circulating water once the control temperature is reached. Patient core body temperatures are currently being maintained at 41·8°C±0·1°C for time periods of up to four hours.