Lemon fruits have a non-uniform histological structure, and are characterized by abundant volatile compounds. However, the distribution of volatile compounds in different tissues remain unknown. Herein, electronic nose (E-nose) and headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME-GC-MS) were employed to qualitatively and quantitatively analyze the volatile compound content in different tissues of fresh lemon fruits, while their microstructures were observed using several microscopy methods. The numbers of volatile compounds detected in the flavedo, albedo, juice vesicles, and segment wall were 41, 23, 29, and 19, respectively. The volatile compounds detected in the four tissues were mainly alkenes, alcohols, aldehydes, esters, and ketones, with a significant descending order in the total content (p < .05). The measurements of E-nose and HS-SPME-GC-MS both showed that the highest total content of volatile compounds was in the flavedo, followed by albedo, juice vesicles, and segment wall (p < .05). Furthermore, oil sacs and oil droplets were only observed in the flavedo by microstructure observation, where more essential oils (mainly volatile compounds) were distributed. The microstructure observation results also verified the measurement results of the E-nose and HS-SPME-GC-MS. These findings provide basic data for sensory evaluation and the comprehensive processing and utilization of lemon fruits.

Based on the simulation results of the typical rural ultra-low energy building (ULEB) in five different climatic regions of China, three indicative technical parameters for paralleled-loop exhaust air heat pump (PEAHP) R&D which are nominal heating-cooling capacity, maximum required fresh air to return air ratio (MFRR) and system energy efficiency grades were calculated and summarized according to the demand of indoor thermal comforts by using statistic method. The nominal heating-cooling capacities were determined according to the peak loads, which are 6.84-2.01 kW, 5-2.96 kW, 3.9-4.6 kW, 3.08-5.02 kW, and 3.4-0.46 kW in the ULEB of Harbin, Beijing, Shanghai, Guangzhou, and Kunming, respectively. To ensure both thermal comforts and energy conservation, during the heating season, full fresh air supply is suggested in Beijing and the 1:0.5 MFRR is suggested in Harbin, Shanghai, Guangzhou, and Kunming. During the cooling season, the 1:5 MFRR is suggested in Shanghai and Guangzhou, the 1:3, 1:1.5, and 1:0.5 MFRR are suggested in Harbin, Beijing and Kunming, respectively. The PEAHP energy efficiency grades 1~5 are 7.92~11.7, 7.58~11.5, 7.5~11.35, 6.12~9.27, and 4.64~7.03 during the heating season of Harbin, Beijing, Shanghai, Guangzhou, and Kunming, respectively, and are 2.33~3.54, 3.93~5.96, 4.61~6.98, 4.62~6.99, and 2.04~3.1 for the cooling season, respectively.

In the data center, using ambient energy cooling technology can effectively reduce the average power use efficiency, and the heat pipe as an effective use of ambient energy device has attracted much attention. For the dynamic heat pipe, reducing the power consumption of the pump effectively is the key to improving the efficiency. In this paper, the rotary booster is selected as the gas phase booster device of the heat pipe unit, the standard unit of the rotary booster is improved, and three types of boosters are obtained, including two improved boosters and one standard unit. Comparative test studies are conducted on three different types of boosters, and the power of the booster shows a downward trend with the increase in indoor and outdoor temperature differences (outdoor temperature decreases). With the increase in indoor and outdoor temperature differences, the cooling capacity increases first and then decreases. When the indoor and outdoor temperature difference is greater than 20 °C, the suction pressure of the booster is greater than the saturated condensing pressure force under outdoor ambient temperature, and the work of the booster decreases. Among the three types of boosters, the medium pressure ratio booster energy efficiency ratio (EER) is the largest. After throttling the standard unit, results show that its cooling capacity unit increases, but the booster power also increases, and the EER is still smaller than that of the improved unit.