用于农业温室集热调温的太阳能热水器

介绍一种用于农业温室集热调温的太阳能热水器研制及其试验情况。     

农业温室太阳能集热调温系统的研究及其进展

综述了国内外农业温室太阳能集热调温系统的研究方法和研究情况,并在此基础上,根据作者对云南农村经济发展水平和气候状况的分析介绍了作者自己的研究思路及初步研究成果。     

温室太阳能热水系统夏季调温性能的研究

温度是动植物生长的重要生态条件之一,为了获得最佳的作物生长温度,抵御室外的极端气候条件,温室必须配备合适的增温和降温系统。对大多数温室来说,夏季白天采用换气、遮光、洒水、室内喷雾就可以降温[1]。农业温室增温和降温消耗的能源接近欧洲能源总预算的1.5%,在南欧国家,增温消耗占温室总运行费用的30%[2]。近十年来,采用太阳能替代常规能源为温室加热,已     

三维立体式太阳热水器及其集热盲区

文中给出了三维立体式太阳热水器,并由实验证明了三维立体式太阳热水器的热效率高于平板型太阳热水器,同时给出了在不同纬度地区的集热盲区的计算方法。要提高热效率,必须避开集热盲区。     

太阳能建筑构件--真空管集热保温板

我们认为要使太阳热水器真正与建筑有机地结合在一起，最好是从设计入手，把热水器作为建筑的一个组成部分，即建筑构件，以满足建筑的基本要求为前提进行设计，设计、生产出用于“建筑。的太阳热水器。     

新型集热蓄热被动式太阳房

介绍了一种用蓄热材料建成的南向集热蓄热被动式太阳房结构和和特性,利用平板式空气太阳能集热器的特性方程分析,得出了室内温度分布的瞬态方程,并分析了该太阳房在沈阳地区24h室温及室内壁温的平均波动,根据计算,该太阳房比传统房节能96％。     

太阳能蓄热系统提高温室地温的试验研究

利用太阳能代替煤炭对温室内地温进行增温，在加热方式上提出地下蓄热、加热系统，并与传统的煤炉地上加热方式进行比较。经过一个黄瓜生长季节的实验得出：太阳能地下蓄热、加热系统温室与煤炉地上加热系统温室相比，地温平均提高4．4℃，产量提高21％以上。由此可见，利用太阳能地下蓄热、加热系统不但能有效地提高温室内地温以提高作物产量，还能替代化石燃料的使用而减少CO、CO2、SO2、NOx等有害气体的排放量，能够取得较好的经济效益和环境效益。     

温室增温节能措施

温室增温节能措施黑龙江省冬季漫长，气候严寒，最低气温在－３０℃以下，温室生产蔬菜需用煤炉加热４个多月，而当地煤价很高，因此温室采取增温节能措施十分重要。一、温室的设计与建造温室要建造在背风向阳的地方，北侧利用天然屏障或建筑物，或加防风屏障，这对保温有...     

Modeling the heat balance of a solar greenhouse with a passive heat accumulator

A model of heat balance of a solar greenhouse with a passive water accumulator in the system soil-plants-heat accumulator-air-fencing-atmosphere is presented. The heat of moisture evaporation from the soil surface and plants is defined using the Bowen-Penman method.     

Passive proliferation of convective heat transfer consummated with nanoporous surface

This paper analyses the passive augmentation of convective heat transfer administering the nanoporous layers fabricated by electrochemical anodization and spray pyrolysis. Nanoporous structures fabricated in electrochemical anodization have pore size varying from 40 to 120 nm, and the pore size procured in spray pyrolysis fluctuates from 60 to 100 nm. Convective energy transfer greatly banks on surface attributes. These nanoporous structures aid in hindering the dynamic flow of fluid and the turbulence is achieved more expeditiously. The proliferation of the convective heat transfer obtained with electrochemically anodized nanoporous surface is 131% higher than the polished bare metals with surface roughness 0.2 μm. In case of spray pyrolysis the maximum proliferation is 120%. Disparate disciplines of nanoporous fabrication are perused for asserting a productive process. This paper also analyses the control parameters in the nanoporous fabrication process.     

Numerical and experimental analysis of convection heat transfer in passive solar heating room with greenhouse and heat storage

In this paper, heat transfer and air flow in passive solar heating room with greenhouse and heat storage are studied. Thermal insulation of solar heating room has significant effects on temperature distribution and airflow in the heating chamber of this solar system. Heat transfer and air flow in a rock bed, which is used as solar absorber and storage layer, are also studied. If porosity is kept within certain range, increasing the rock size causes an increase of the capability of thermal storage and heating effects; increasing the porosity of thermal storage materials results in an increase of the bed temperature but a decrease of the rock mass. The specific heat capacity and thermal conductivity have a remarkable effect on the average temperature of rock bed. All these factors should be taken into account when designing a solar heating system.     

Numerical study of greenhouse nocturnal heat losses

In this study we quantify and analyze different components of nocturnal losses from a heated greenhouse with the presence of vegetation for typical winter weather conditions in Marrakesh-Morocco,using a non linear model,based on the greenhouse heat and mass balance.It was found that 12% of the total input heat was dissipate as a sensible and latent leakage losses,66% was lost by convective exchange through air-inner cover.This gain of energy at the inner-cover is dissipated at the outer-cover by radiation(66%)and convection(34%).This results point toward some practical measures to reduce heat losses:increasing air tightness,using covering materials with low-emissivity in the long wave band or putting up an external thermal curtain should provide significant energy savings.     

多壁碳纳米管-乙二醇纳米流体集热性能研究

为研究多壁碳纳米管-乙二醇纳米流体(MWCNTs-EG)的集热能力,采用单层玻璃管作为集热管,对6种不同体积分数、不同颗粒粒径的MWCNTs-EG流体和水进行了闷晒集热实验。测试表明,相同体积分数的MWCNTs-EG流体的集热温度随着颗粒粒径的增大而增大,其瞬时集热量最高可达54.2k J,是水集热量的2.4倍。其中,MWCNTs-EG(30~50nm,0.06vol%)的温升最为明显,最大平均值是53.8℃,温升为22.7℃。此外,MWCNTs-EG的体积分数、颗粒粒径以及其团聚沉降均能影响着纳米流体的集热效果。     

Passive heat and moisture removal from a natural vented enclosure with a massive wall

Simultaneous transport of heat and moisture by conjugate natural convection in a partial enclosure with a solid wall is investigated numerically. Moist air motions are driven by the external temperature and concentration differences imposed across enclosures with different ambient moisture conditions. The Prandtl number and Schmidt number used are 0.7 and 0.6, respectively. The fluid, heat and moisture transports through the cavity and solid wall are, respectively, analyzed using the streamlines, heatlines and masslines, and the heat and mass transfer potentials are also explained by the variations of overall Nusselt and Sherwood numbers. The numerical simulations presented here span a wide range of the main parameters (heat and mass diffusion coefficient ratios, solid wall thickness and thermal Rayleigh numbers) in the domain of aiding and opposing buoyancy-driven flows. It is shown that the heat transfer potential, mass transfer potential, and volume flow rate can be promoted or inhibited, depending strongly on the wall materials and size, thermal and moisture Rayleigh numbers.     

Radiation and heat characteristics of plant leaves in a solar greenhouse

The paper considers spectral absorption characteristics of the middle leaf of agricultural plants. A model of heat balance in the plant-air-soil-fence leaf system in conditions of a greenhouse is given.     

Transient response of latent heat storage in greenhouse solar system

A latent heat storage system with two different stacking configurations and air bafflings was designed and constructed as an integrated part of the greenhouse solar system (solar barn). Commercial cylindrical storage rods were used as the primary storage elements. The results showed that the designed latent storage systems demonstrated significantly higher compact storage capacity than water or rock storage and that the ring-baffled storage unit performed better than the cross-baffled storage unit.     

Analysis of flow and heat transfer characteristics of porous heat-storage wall in greenhouse

The flow and heat transfer characteristics of porous heat-storage wall in greenhouse are studied by using the one-dimensional steady energy two-equation model for saturated porous medium. The results show that the heat exchange between the air and the solid matrix of the porous heat-storage wall depends upon the inlet air velocity, the porosity and the permeability of porous medium, and the thermal conductivity of the solid matrix. Because the incidence of solar radiation on the porous heat-storage wall is not uniform, the new composite porous solar wall with different porosity is proposed to reduce the disadvantageous effect. __________ Translated from Journal of Engineering Thermophysics, 2008, 29(2): 284–286 [译自: 工程热物理学报]