An investigation of a heat pump system using CO2/propane mixture as a working fluid

In order to decrease the heat rejection pressure of heat pump using pure working fluid, CO₂ or R744, other natural component including hydrocarbons (R290, R600a, R600, R1270, R170, R601) and dimethyl ether (RE170) is added to CO₂, respectively, and then six binary mixtures are achieved. By environmental and thermodynamic comparisons, R290 is selected to be the most appropriate component candidate to mix with CO₂, and meanwhile to weaken the flammability and explosivity for pure R290. Then, the system performances of heat pump using mixture of CO₂ and R290 were experimentally studied when R290 is added to CO₂ with a small fraction, and compared with that of the pure CO₂. The experimental test rig is designed and set up for the transcritical heat pump system. When the refrigerant charge is variable, the heating coefficient performance, optimum heat rejection pressure, compressor power, mass flow rate of refrigerant, and total heat coefficient of gas cooler were researched. The variation ratios of heating coefficient performance and heating capacity with deviation from the optimum refrigerant charge were also investigated. The optimum refrigerant charge of CO₂/R290 is obtained and the research results show that the addition of R290 to CO₂ can efficiently reduce the heat rejection pressure and improve the system performance. The results in the present work could provide useful guidelines for the design and operation of heat pump system using CO₂-based mixture.     

The influences of recycle effect on double-pass V-corrugated solar air heaters

The study of the heat transfer enhancement for the recycling double-pass V-corrugated solar air heaters, which implement the external recycle of flowing air, was investigated experimentally and theoretically. The comparison among different designs of V-corrugated, baffled and fins attached, and flat-plate collectors was made to show the device performance improvement with various operating parameters under the same working dimensions. The recycling double-pass V-corrugated device developed here was proposed in aiming to strengthen the convective heat-transfer coefficient and enlarge the heat transfer area. The error analysis of experimental results deviate by 0.85–2.46% from the theoretical predictions with the fairly good agreement, and both results show that the device performance of the recycling double-pass V-corrugated operation is better than those of the other configurations under various recycle ratios and mass flow rates. The suitable selections were obtained for operating recycling double-pass V-corrugated devices while considering with an economic viewpoint by both the collector efficiency enhancement and the power consumption increment.     

An experimental and a numerical study of horizontal earth-air heat exchanger in a hot climate

Earth-air heat exchangers (EAHE) are devices used in the geothermal technique in order to reduce energy consumption in buildings. In this study, a simulation was conducted through the computational fluid dynamics platform FLUENT 6.3 for the prediction of thermal performance of the EAHE that describes the variation of the air temperature inside the tube. For this, it was necessary to design the heat exchanger while respecting the design and the actual dimensions of the experimental set-up, and stating that the temperature of the wall of the horizontal tube of the exchanger is equal to that of ground at 3 m depth. It should be noted that in assessing the temperature along the two sections vertical (input and output) of the exchanger, opting for a function (UDF) the user define function. Finally, noting a good agreement between both experimental and numerical study, and showing that a significant reduction in temperature at the outlet of the exchanger to a difference of 20 °C, confirming the effectiveness of the heat exchanger.     

东北玉米热量指数预测方法研究(Ⅰ)——热量指数与玉米产量

利用东北地区典型站点1961-2005年气象资料和东北3省1961-2005年玉米产量资料,计算分析了东北不同地区玉米热量指数的变化趋势以及与产量的关系。结果表明：受气候变暖的影响,辽宁省热量指数出现下降的趋势,而吉林省和黑龙江省的热量指数出现显著升高的趋势,气候变暖对吉林省和黑龙江省玉米生产有有利的影响。热量指数较好地反映了玉米产量与环境温度的相关关系。因此,可通过对玉米热量指数的预测进行农作物低温冷害预测,为农业生产防灾减灾提供决策依据。     

Integration of traditional and innovative characterization techniques for flux-based assessment of Dense Non-aqueous Phase Liquid (DNAPL) sites

Key attributes of the source zone and the expanding dissolved plume at a trichloroethene (TCE) site in Australia were evaluated using trends in groundwater monitoring data along with data from on-line volatile organic compound (VOC) samplers and passive flux meters (PFMs) deployed in selected wells. These data indicate that: (1) residual TCE source mass in the saturated zone, estimated using two innovative techniques, is small ( 10 kg), which is also reflected in small source mass discharge ( 3 g/day); (2) the plume is disconnecting, based on TCE concentration contours and TCE fluxes in wells along a longitudinal transect; (3) there is minimal biodegradation, based on TCE mass discharge of  6 g/day at a plume control plane  175 m from source, which is also consistent with aerobic geochemical conditions observed in the plume; and (4) residual TCE in the vadose zone provides episodic inputs of TCE mass to the plume during infiltration/recharge events. TCE flux data also suggest that the small residual TCE source mass is present in the low-permeability zones, thus making source treatment difficult. Our analysis, based on a synthesis of the archived data and new data, suggests that source treatment is unwarranted, and that containment of the large TCE plume ( 1.2 km long,  0.3 km wide; 17 m deep;  2000–2500 kg TCE mass) or institutional controls, along with a long-term flux monitoring program, might be necessary. The flux-based site management approach outlined in this paper provides a novel way of looking beyond the complexities of groundwater contamination in heterogeneous domains, to make intelligent and informed site decisions based on strategic measurement of the appropriate metrics.     

Gaseous mercury emissions from unsterilized and sterilized soils: The effect of temperature and UV radiation

Mercury (Hg) emissions from the soils taken from two different sites (deciduous and coniferous forests) in the Adirondacks were measured in outdoor and laboratory experiments. Some of the soil samples were irradiated to eliminate biological activity. The result from the outdoor measurements with different soils suggests the Hg emission from the soils is partly limited by fallen leaves covering the soils which helps maintain relatively high soil moisture and limits the amount of heat and solar radiation reaching the soil surface. In laboratory experiments exposure to UV-A (365 nm) had no significant effect on the Hg emissions while the Hg emissions increased dramatically during exposure to UV-B (302 nm) light suggesting UV-B directly reduced soil-associated Hg. Overall these results indicate that for these soils biotic processes have a relatively constant and smaller influence on the Hg emission from the soil than the more variable abiotic processes.     

Are Bavarian Forests (southern Germany) at risk from ground-level ozone? Assessment using exposure and flux based ozone indices

Exposure and flux-based indices of O₃ risk were compared, at 19 forest locations across Bavaria in southern Germany from 2002 to 2005; leaf symptoms on mature beech trees found at these locations were also examined for O₃ injury. O₃ flux modelling was performed using continuously recorded O₃ concentrations in combination with meteorological and soil moisture data collected from Level II forest sites. O₃ measurements at nearby rural open-field sites proved appropriate as surrogates in cases where O₃ data were lacking at forest sites (with altitude-dependent average differences of about 10% between O₃ concentrations). Operational thresholds of biomass loss for both O₃ indices were exceeded at the majority of the forest locations, suggesting similar risk under long-term average climate conditions. However, exposure-based indices estimated higher O₃ risk during dry years as compared to the flux-based approach. In comparison, minor O₃-like leaf injury symptoms were detected only at a few of the forest sites investigated. Relationships between flux-based risk thresholds and tree response need to be established for mature forest stands for validation of predicted growth reductions under the prevailing O₃ regimes.     

Persistence of radon-222 flux during monsoon at a geothermal zone in Nepal

The Syabru-Bensi hydrothermal zone, Langtang region (Nepal), is characterized by high radon-222 and CO₂ discharge. Seasonal variations of gas fluxes were studied on a reference transect in a newly discovered gas discharge zone. Radon-222 and CO₂ fluxes were measured with the accumulation chamber technique, coupled with the scintillation flask method for radon. In the reference transect, fluxes reach exceptional mean values, as high as 8700 ± 1500 g m⁻² d⁻¹ for CO₂ and 3400 ± 100 × 10⁻³ Bq m⁻² s⁻¹ for radon. Gases fluxes were measured in September 2007 during the monsoon and during the dry winter season, in December 2007 to January 2008 and in December 2008 to January 2009. Contrary to expectations, radon and its carrier gas fluxes were similar during both seasons. The integrated flux along this transect was approximately the same for radon, with a small increase of 11 ± 4% during the wet season, whereas it was reduced by 38 ± 5% during the monsoon for CO₂. In order to account for the persistence of the high gas emissions during monsoon, watering experiments have been performed at selected radon measurement points. After watering, radon flux decreased within 5 min by a factor of 2–7 depending on the point. Subsequently, it returned to its original value, firstly, by an initial partial recovery within 3–4 h, followed by a slow relaxation, lasting around 10 h and possibly superimposed by diurnal variations. Monsoon, in this part of the Himalayas, proceeds generally by brutal rainfall events separated by two- or three-day lapses. Thus, the recovery ability shown in the watering experiments accounts for the observed long-term persistence of gas discharge. This persistence is an important asset for long-term monitoring, for example to study possible temporal variations associated with stress accumulation and release.     

Recycling and Reusing Heat Energy During the Production of Powdery Phospholipid

The temperature is 56.5℃when acetone gas is rectified during the production of powdery phospholipid. If heat exchanger is added, heat energy that is reclaimed can be used by other heaters. On the basis of exchange hot water （51℃） 4m3 every minute, a factory with the productivity of powdery phospholipid being 10 ton a day can save 533.2 ton standard coal which is equivalent to 746.48 ton common coal. If this technique of saving energy and reducing emission could be widely used in correlative industries of all over the country, economic benefits will be prominent.     

锅炉量化管理是企业挖潜节能的重要途径

通过对辽河油田公司有关企业开展清洁生产审核,总结出了燃料锅炉量化管理的方法。在自然对流烘干室改造、碱液浓缩炉改造、燃煤锅炉设计效率核准等实例中,该方法可昭示能耗大的"瓶颈"部位,进而为企业制定节能方案、提出具体的节能改造措施提供了科学依据。实践证明:实施锅炉量化管理是企业挖掘节能潜力的重要途径。