THERMAL-CHARACTERISTICS OF A HOOP STRUCTURE FOR SWINE PRODUCTION

The thermal performance of a low-cost, hoop-type swine building (3.55 x 5.7 x 10.3 m) was evaluated under the winter weather conditions of C entral Japan. The hoop building had two curved roofs made from 2.5 cm diameter tubular steel pipes each covered with a reflective film. Ther e wets a 20 cm air space between the inner and outer covers through wh ich the exhaust air flowed. A positive-pressure ventilation fan and an air distribution duct were used to supply the fresh air The evaluatio n was conducted for three opening configurations of the air distributi on duct (one, two, or four holes on a cross-section of the duct) and p resence or-absence of an internal curtain. Furthermore, the effect of replacing the reflective film with a PVC film for the east side cover on solar transmission and thus the internal temperature rise was quant ified. The building was simulated to house 30 pigs at a body weight of 70 kg. Resistive heating wire was used to simulate the sensible heat generation of the pigs at 131.5 W/pig at 10 degrees C temperature. The inside temperature averaged 6.9 degrees C higher than the outside tem perature during the minimum ventilation period As the exhaust air pass ed through the double-layer air space, 25.4% of exhaust heat transferr ed back into the building and 74.6% lost to the outside. When replacin g the reflective covers with the PVC film covers on the east side, the internal temperature rise increased to an average of 7.6 degrees C wi th a maximum of 12.7 degrees C. The magnitude of temperature rise was proportional to the transmitted solar radiation, as evidenced by the h igher temperature rise during the day and significantly reduced temper ature rise at night. To eliminate the effects of cold, nocturnal radia tion, the PVC film cover should be covered by the regular reflective c over at night. One-holed air duct had a tendency to produce drafts in the pig occupied zone (POZ, 1.2 x 0.7 m), whereas four-holed air duct tended to have less mixing effects on the ail: In comparison, the comb ination of two-holed air duct and use of the internal curtain was foun d to be the best in achieving warmer air temperature and minimizing dr afts in POZ.