Effect of pipes in heat pump system on electric vehicle energy saving

ABSTRACT

Refrigerant pressure drop and temperature change in pipes are normally ignored in the thermodynamic analysis of traditional vehicle air conditioning system, this will result in serious errors. In this Paper, pressure drop and temperature difference are simulated in different pipes of electric vehicle (EV) heat pump system to analysis the effects of pipes in the actual EV heat pump system. The results indicate that the greater the mass flow, the faster pressure drop increases, the temperature difference decreases. Pressure drop of saturated liquid refrigerant is smaller than that of saturated gas refrigerant at the same saturation pressure and mass flow rate. The higher the refrigerant pressure (no phase change), the slower pressure drop decreases, the faster the temperature difference decreases. Pressure drop decreases with the increment of bending angle of the pipe. For EV heat pump system, suitable valves and less branches are helpful for energy saving of the system. Shortening the pipe between compressor and condenser can reduce temperature change obviously. Pressure drop per unit length in the pipe between evaporator and compressor is large especially in heating mode because of lower refrigerant density. It even reaches to over 100 times of that in the pipe between condenser and throttle valve in heating mode and has negative effects on the performance of the system. If the evaporator is closer to the compressor and the number of branches is less, then pressure drop will decrease a lot, which will be advantageous for energy saving of the heat pump system.     

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.     

重庆市应用湖库水水源热泵系统条件分析

通过对重庆市气候条件、湖库水水资源状况以及湖库水水温和水质分析,结果显示:重庆地区采用传统空气源热泵系统已不适宜,而采用水源热泵系统具有较高的节能优势。丰富的湖库水水资源量以及重庆市建筑沿湖库水而建特点,为在重庆市开展湖库水水源热泵系统创造便利条件;湖库水水温和水质基本能满足地表水水源热泵系统的水源要求;湖库水藻类易爆发,因此发展湖库水水源热泵主要解决的水质问题是藻类的堵塞问题。     

A CLOSED WATER REUSE SYSTEM FOR POWER PLANT COOLING AND DIGESTER HEATING1

ABSTRACT: A model consisting of closed water reuse and productive use of various types of wastes for energy generation is presented. The sewage after treatment would be used as the cooling water for power plants, and the condenser discharge therefrom be used as heating water for sludge digesters. The water is then purified for municipal water supply for continuous use. The advantages of this system are that water resources and energy are conserved while various types of wastes including waste heat are controlled. With a preliminary system analysis, it appears that the design for power plant based on the total heating value of wastes and digester capacity based on sewage sludge generation is feasible in terms of acquisition and full utilization of various types of wastes as generated in a single metropolitan area. The system as shown in this design is in balance among various factors such as the generation rate of municipal refuse, municipal sewage, waste heat in the condenser discharge, and raw sewage sludge.     

HYDROLOGICAL AND GEOCHEMICAL TRENDS AND PATTERNS IN THE UPPER RIO GRANDE, 1975 TO 19991

ABSTRACT: Hydrological and geochemical spatial patterns and temporal trends were analyzed using U.S. Geological Survey (USGS) water quality data collected from 1975 to 1999 along the uppermost 600 km of the Rio Grande in Colorado and New Mexico. Data on discharge, specific conductivity (SC), total dissolved solids (TDS), pH, Ca²⁺, Na⁺, Mg²⁺, K⁺, HCO₃^?, SO₄^2‐, Cl^?, F^?, and SiO₂ came from six USGS stations ranging from the Colorado‐New Mexico border to below Albuquerque, New Mexico. Linear regression, Kendall's S, and Seasonal Kendall's S’ were used to detect trends, and ANOVA was used to analyze spatial differences between stations. Statistically significant increasing trends occurred in SC, TDS, Ca²⁺, Na⁺, Mg²⁺, K⁺, Cl^?, and F^?in the uppermost reaches, and significant decreasing trends of SC, TDS, Ca²⁺, Mg²⁺, K⁺, HCO₃^?, and SO₄^2‐occurred at the lower stations around Albuquerque. Both fluoride concentrations and pH values increased at and below Albuquerque over the study period. Discharge data show an increasing trend across all stations. Spatially, data for dissolved substances show generally linear upstream to downstream increases in concentrations in the upper four stations, with several notable nonlinear increases at and below Albuquerque (SC, TDS, Na⁺, Cl^?). Significant increases in pH appear at and below Albuquerque, relative to upstream stations, probably due to improved sewage treatment.     

Off-design performance analysis of a transcritical CO2 Rankine cycle with LNG as cold source

The transcritical CO₂ Rankine cycle with liquefied natural gas (LNG) as cold source is a promising power system to utilize mid- and low-temperature heat source. Most previous works focused on thermodynamic and thermoeconomic analysis or optimization for the system. In this article, an off-design performance analysis for the system is conducted. An off-design mathematical model for the system is established to examine the variation of system performance with the variations of heat source mass flow rate and temperature. A modified sliding pressure regulation control strategy, which regulates turbine inlet pressure to keep the temperature difference between heat source temperature and turbine inlet temperature constant, is applied to control the system when off-design conditions happen. The results show that when the mass flow rate or the temperature of heat source is less or lower than that of design condition, both the net power output of system and the system exergy efficiency decrease, whereas when they are more or higher than the values of design condition, the net power output of system increases but the system exergy efficiency still decreases. In addition, both CO₂ turbine and NG turbine could almost keep the designed efficiency values under the applied control strategy.     

新疆地区地温采暖技术的应用探讨

针对寒冷地区建筑物的采暖方式，介绍一种新型的区域供暖方式－－地温水源热泵（地温中央空调）供暖系统，为寻找新型供暖方式提出了环保安全、绿色节参采暖制冷新理念。     

ALGAL BIOASSAY AND GROSS PRODUCTIVITY EXPERIMENTS USING SEWAGE EFFLUENT IN A MICHIGAN WETLAND'

ABSTRACT: One component of the filamentous algal community of a northern fen ecosystem in central Michigan was studied under conditions of nutrient enrichment by secondarily treated sewage effluent during one growing season. The productivity of Cladophora spp. measured by continuous flow bioassay was 2.6 g dry weight m day at the site of effluent addition compared to 0.085 g m day at the control site. Under conditions of nutrient enrichment, uptake by bioassay Cladophora spp. averaged 12 mg m^?2day^?1for phosphorus and 55 mg m^?2day^?1for nitrogen, compared to 0.01 mg m^?2 day^?1and 0.16 mg m^?2day^?1for phosphorus and nitrogen, respectively, in the control area. At the end of the growing season approximately 4.3 g N m^?2 and 0.96 g P m^?2were immobilized in Cladophora algal biomass. Algal growth temporarily immobilized 3.0 percent of the nitrogen and 1.0 percent of the phosphorus added as sewage effluent. Gross productivity of surface water in the fen averaged 1.5 g O₂m^?2day^?1at the nutrient enriched site, compared to 0.5 g O₂ m^?2day^?1at the control area. Gross productivity, community respiration and reaeration constant values in the fen were similar to data collected by other researchers in shallow water aquatic systems, but only at the fertilized sites.     

EVAPOTRANSPIRATION FROM A BULRUSH‐DOMINATED WETLAND IN THE KLAMATH BASIN,OREGON1

ABSTRACT: Growing‐season evapotranspiration and surface energy and water balances were investigated for an extensive, bulrush‐dominated wetland in the Upper Klamath National Wildlife Refuge of south‐central Oregon, a semi‐arid region with competing demands for scarce water resources. Turbulent fluxes of sensible and latent heat were measured by eddy covariance for 1.2 to 1.9 days during each of four site visits during late‐May to mid‐October 1997. Mean daytime latent heat flux and the Bowen ratio ranged from 148 to 178 W m^?2 and from 0.38 to 0.51, respectively, during late May, mid‐July, and late August site visits. By mid‐October, when the plant canopy had senesced, daytime latent heat flux and the Bowen ratio averaged 46 W m^?2 and 2.8, respectively. An hourly Penman‐Monteith (PM) model that was fitted to the surface‐flux data provided values for the surface resistance to water‐vapor diffusion that ranged from 78 s m^?1 during late August to 206 s m^?1 during mid‐October. Similarly, a Priestley‐Taylor (PT) model provided values for the PT multiplier (a) that ranged from 0.96 during late August to 0.37 during mid‐October. The PM and PT models predicted evapotranspiration totals of 560 and 480 mm, respectively, for May 28 to October 12, 1997.     

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.     

SELECTED NUTRIENTS AND HEAVY METALS IN SEWAGE SLUDGE FROM NEW JERSEY POTWs1

ABSTRACT: In order to determine appropriate application rates and to ensure low pollutant levels in sewage sludge, knowing the chemical composition of sewage sludge is of great importance in a land application program. The objective of this study is to evaluate the variability of selected chemical characteristics of sewage sludge from New Jersey publicly owned treatment works (POTWs). Measurements of total Kjeldahl nitrogen (TKN), NH₄⁺‐N, P, K⁺, Cd, Cu, Pb, and Zn reported by 98 facilities in the 1996 and 1997 New Jersey Sludge Quality Assurance Regulations (SQAR) reports were statistically analyzed. Sewage sludge from Category 5 POTWs (greater than 10 percent industrial input) showed higher Cd, Cu, and Pb concentrations than Category 3 and Category 4 facilities (less than 10 percent industrial input). Even though only two years of data were analyzed, there was an indication that Cd and Pb concentrations in sewage sludge are decreasing with time. The yearly mean of only a few facilities exceeded the federal pollution concentration limits (40 CFR Part 503, Table 3). Phosphorus and Cd values showed the highest variability within facilities based on the coefficient of variation. Due to the variability of sewage sludge constituents, the use of the yearly rolling mean of nutrient concentrations to determine application rates was considered inadequate. An actual analysis of the sewage sludge to be applied is more appropriate to determine application rates than historical data.     

Application of treated wastewater and digested sewage sludge to obtain biodiesel from Helianthus annuus L. seeds oil

Waste from wastewater treatment plants (WWTP) for Helianthus annuus L. production may be a viable solution to obtain biodiesel. This study achieved two objectives: assess the agronomical viability of waste (wastewater and sludge) from the Alcázar de San Juan WWTP in central Spain for H. annuus L. production; use H. annuus L. seeds grown in this way to obtain biodiesel. Five study plots, each measuring 6 m × 6 m (36 m²), were set up on the agricultural land near the Alcázar de San Juan WWTP. Five fertilizer treatment types were considered: drinking water, as the control; treated wastewater; 10 t ha^?1 of air-dried sewage sludge; 20 t ha^?1 of air-dried sewage sludge; 0.6 t ha^?1 of commercial inorganic fertilizer. Soil, irrigation water, sewage sludge, crop development and fatty acid composition in achenes oil were monitored. The 20 t ha^–1 dose of sewage sludge proved effective to grow H. annuus L. with similar results to those grown with a commercial fertilizer. However, precautions should be taken when irrigating with wastewater because of high salinity and nutrient deficiency. Sunflower oil was composed mostly of linoleic and oleic acid. The remaining fatty acids were linolenic, estearic, nervonic, palmitoleic, and palmitic.     

Refrigeration waste heat utilization for drying applications: a review

ABSTRACT

Cold chain industry has a vast potential for waste heat recovery. It is a matter of importance for energy efficiency point of view, as global energy demand is increasing day by day. Ample amount of low-grade energy is either unutilized or underutilized. The heat rejected by a Heat pump or refrigeration system emerged as a promising solution for dehydration by utilizing low-grade waste heat despite higher investment. As compared to solar drying technology, heat pump drying evolved as a reliable method regarding better process control, energy efficiency, and quality of the product to be dried. Energy utilized through the refrigeration system’s waste/exhaust heat recovery in combination with or without renewable energy source enhances the overall efficiency of the system and also reduces the cost. This useful review investigated and compared the research findings of waste heat utilization through heat pump and from condenser of refrigeration system on laboratory, pilot as well as industrial scale for drying of various fruits, vegetables, and agro products. Various drying parameters like drying rate, moisture content, Specific Moisture Extraction Rate (SMER), Coefficient of Performance (COP), Exergy efficiency, and temperature as well as humidity conditions inside the drying chamber were also reviewed to promote the technological advancement of energy utilization by commercial cold storage waste heat recovery.     

我国油田产出水再利用技术现状及展望

随着我国油气田勘探开发力度加大和新环保法的实施,油田开采过程中耗水量大和污水处理问题是我国油气田企业面临的共同难题。从污水余热回收、污水回注、压裂液重复利用、钻井废水再利用四个方面,介绍了国内油田产出水再利用技术研究进展与应用现状,指出目前存在的污水余热再利用应用范围不广、回注污水利用不合理、化工原料未回收利用等主要问题。并通过文献调研,展望了油田污水再利用技术的发展方向,指出需从污染源头防控入手,研发更加经济环保的液体配方,并深入研究从污水中取热、取水及取化工原料的循环再利用技术,因地制宜制定相应的水质及污水配伍性实验评价标准,实现从源头至末端治理相结合的油田污水清洁生产。     

Modeling of Low Temperature Geothermal District Heating Systems

Abstract

In this work, low temperature geothermal district heating systems with heat pumps have been studied and compared with fuel-oil boiler heating systems for intermittent and continuous regimes according to the optimum indoor air temperature and operational cost. Izmir Institute of Technology (IZTECH) Campus is taken as a case study. Various heat pump and boiler configurations are studied to meet required duty. Operational cost analysis for each alternative is conducted. According to the results, for IZTECH Campus the best alternative, which gives the optimum indoor air temperature and the lowest operational cost, is heat pump continuous regime.     

Numerical parametric study of a new earth-air heat exchanger configuration designed for hot and arid climates

ABSTRACT

Thermal potential for cooling and heating can be achieved by new configuration of earth–air heat exchanger (EAHE). This paper presents a numerical investigation of thermal performance of a spiral-shaped configuration of EAHE intended for the summer cooling in hot and arid regions of Algeria. A commercial finite volume software (ANSYS FLUENT) has been used to carry out the transient three-dimensional simulations and the obtained results have been validated using the experimental and numerical data obtained from the literature. The agreement between our simulation results and those from literature is very satisfactory. A parametric analysis of the new geometry of (EAHE) has been performed to investigate the effect of pitch, depth, pipe length and of the flow velocity on the outlet air temperature and the EAHE’s mean efficiency as well as its coefficient of performance (COP). It has been shown that when the pitch space varies between 0.2 and 2 m the difference of outlet air temperature increases by 6 ^°C. When the air velocity increases from 2 to 5 m/s the mean efficiency decreases from 60 % to 33 % and the COP of the EAHE decreases from 2.84 to 0.46.     

Simulation and validation of a suitable model for thin layer drying of ginger rhizomes in an induced draft dryer

Variation in drying material and their biological differences, coupled with heat supply method in different dryers, makes mathematical modeling of drying complicated. Attempt was made to simulate a drying process and to identify best suitable model out of six selected drying models, for drying of ginger slices in a solar-biomass integrated drying system designed and developed for spice drying. Moisture content data were converted into the moisture ratio (MR) expressions and curve fitting with drying time for the selected drying models was analyzed. Sigma Plot software was used for nonlinear regression to the data obtained during drying and for modeling of drying curves. The suitability of the models was evaluated in terms of statistical parameters such as coefficient of determination (R²), mean percentage error (P), and standard error estimate. Drying air temperature was in the range of 47–55°C and air velocity was between 1.0 and 1.3 m s^?1. Ginger slices were dried from 88.13% to 7.65 ± 0.65% (wb) in 16 h. Trays were interchanged in a predetermined matrix sequence from 4 h onwards when moisture content was reduced to 60–70% (wb), for uniformity in drying. Highest value of R² (0.997), lowest value of SEE (0.020), and P value < 0.0001 established Page model as the best suitable model for the developed drying system. The predicted MRs were in good agreement with the experimental values and the effective moisture diffusivity for ginger was found to be 2.97 × 10^–7 m² s^?1.     

城镇生活污水治理规划研究——以双阳区奢岭镇为例

实现农村生活污水有效治理在推进生态文明建设和农民生活方式现代化中具有标志性意义.通过对区域现状数据调研及分析,划分区域污水汇水分区及选择污水收集方式,合理确定用水指标和污水排放系数,预测生活污水量,布局生活污水处理设施建设.其结果表明:具备条件排入奢岭镇污水处理厂的镇区外村屯的污水,排入奢岭镇区污水处理厂.不具备条件的...     

The convective hot air drying of Lactuca sativa slices

The storage of fresh agricultural products is not easy because of its high moisture. Dehydration is an efficient preservation method. The investigation of drying modeling and transfer characteristics are important for selecting operating conditions and equipment design. The drying behavior of Lactuca sativa slices, with the thickness of 2 mm, was investigated at 60.0–80.0°C and 0.60–1.04 m sec^?1 velocity in a convective hot air drier. The mass transfer during the drying process was described using six thin drying models. The convective heat transfer coefficient α and mass transfer coefficient k_H were finally calculated. The results showed that the drying process could be separated into three stages including accelerating rate, constant rate, and falling rate period, which was influenced by hot air temperature and velocity, and the Modi?ed Page model agreed well with the experimental data. When the operating temperature was increased from 60.0°C to 80.0°C, α was found increased from 88.07 to 107.93 W·m^?2·K^?1, and k_H increased from 46.32 × 10^–3 to 68.04 × 10^–3 kg·m^?2·sec^?1·ΔH^?1. With the increase of air velocity from 0.60 to 1.04 m·sec^?1, α was increased from 78.85 to 101.35 W·m^?2·K^?1, and k_H was enhanced from 51.78 × 10^–3 to 65.85 × 10^–3 kg·m^?2·sec^?1·ΔH^?1.     

PATTERNS OF PERIPHYTON CHLOROPHYLL α IN AN AGRICULTURAL NONPOINT SOURCE IMPACTED STREAM1

ABSTRACT: An agricultural nonpoint source polluted stream in northern Idaho was examined to determine seasonal and longitudinal patterns of periphyton chlorophyll α. Chlorophyll a was measured at eight sites along Lapwai Creek, a fifth order stream impacted by agricultural runoff containing nutrients and eroded soils. Seasonally, periphyton chlorophyll α was lowest in the spring (cumulative x?= 60.4 mg m^?2) and highest in the summer (cumulative x?= 222 mg m^?2). Winter concentrations were higher than expected (cumulative x?= 168.6 mg m^?2). The headwaters, flowing through an open grassy meadow, had the lowest concentrations of the study (two-year x?= 49.7 mg m^?2). Immediately below a small, eutrophic reservoir, periphyton chlorophyll α increased markedly (two-year x?= 155.8 mg m^?2) and remained high through a deep canyon (two year x?= 135.5 mg m^?2) and down to the mouth of the stream (two-year x?= 172.3 mg^?2). Periphyton chlorophyll α in Lapwai Creek was at least two times greater than values reported in the literature for comparable, undisturbed Idaho streams. We suggest that increased nutrient concentrations via agricultural nonpoint source pollution and increased light penetration from the removal of large, woody riparian vegetation have resulted in high periphyton chlorophyll α along the continuum of Lapwai Creek.