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The effect of freezing raw meat on the quality characteristics of beef jerky was evaluated in the present study. Jerky was made using different types of raw beef (fresh, frozen, and frozen-thawed) with different curing times (6 h and 12 h). Frozen-thawed beef had a lower moisture content than fresh or frozen beef due to higher exudate loss (P 0.05). Jerky made using frozen and frozen-thawed beef showed lower drying yield and higher shear force than jerky prepared using fresh beef (P 0.05). Freezing raw beef decreased the fat content and increased the redness, yellowness, chroma, and hue values of jerky (P 0.05). The microstructure of beef jerky was showed to increase the deformation and contraction of muscle fibers due to freezing. Longer curing times increased the moisture content of jerky made using frozen meat (P 0.05). Jerky made using frozen or frozen-thawed meat was tough due to excessive fat and moisture loss.

This paper describes experiments comparing a commercially available R410A heat pump and prototype R744 (carbon dioxide) system in heating mode. The R744 system utilizes aluminum microchannel heat exchangers and a prototype semi-hermetic compressor. System performance is compared for two configurations: first, when the R744 compressor speed is set to match the baseline system’s heating capacity at 8.2 °C outdoors and 21.1 °C indoors; and second, when the air conditioning capacity is matched at 35 °C outdoors and 26.5 °C indoors. The R744 system operates with a slightly lower heating COP, but its higher capacity at lower outdoor temperatures reduces the need for less efficient supplementary heating capacity.

The effect of air inlet humidity condition on the air-side heat transfer and pressure drop characteristics for an inclined brazed aluminum heat exchanger has been investigated experimentally. For a heat exchanger with a louver angle of 27°, fin pitch of 2.1 mm and flow depth of 27.9 mm, a series of tests are conducted for the air-side Reynolds numbers of 80–400, with variation of inlet humidity condition. The heat transfer data are obtained for wet condition only and the pressure drop data are measured for both dry and wet conditions. The inlet air temperature and relative humidity range are 12 °C and 60–90%, respectively. The inclination angles ( θ ) from the vertical position are 0, 14, 45, and 67° clockwise (leeward direction). The inclination angles affect moderately the sensible heat transfer coefficient for wet condition, and the pressure drops for both dry and wet conditions increase systematically with the inclination angle. The heat transfer and pressure drop characteristics under wet condition are not influenced substantially by the air inlet humidity for θ ⩽45°. The effect of the louver directions at the inlet and outlet of the inclined heat exchanger on the performance is also addressed.