Unit TenComfort HeatingHeating SystemA steam (heating) system uses the vapor phase of water to supply heat or kinetic energy through a piping system. As a source of heat, steam can heat a conditioned space with suitable terminal heat transfer equipment such as fan coil units, unit heaters, radiators, and convectors (finned tube or cast iron), or steam can heat through a heat exchanger that supplies hot water or some other heat transfer medium to the terminal units.Water systems that convey heat to or from a conditioned space or process with hot water are frequently called hydronic heating systems. The water flows through piping that connects a boiler, water heater to suitable terminal heat transfer units located at the space or process.Classified by flow generation, hydronic heating systems may be (1) gravity systems, which use the difference in density between the supply and return water columns of a circuit or system to circulate water; or (2) forced systems, in which a pump, usually driven by an electric motor, maintains the flow.Cast-iron RadiatorExpansion TankElectric BoilerRelief ValvePumpReturn PipeCold Water FillSupply PipeRadiatorIn the direct-return system, the length of supply and return piping through the subcircuits is unequal, which may cause unbalanced flow rates and require careful balancing to provide each subcircuit with design flow. Ideally, the reverse-return system provides nearly equal total lengths for all terminal circuits.Solar Altitude and Solar AzimuthSNormalSolar AltitudeSolar Azimuth（偏东为负，偏西为正） The current value of the solar constant (which is defined as the intensity of solar radiation on a surface normal to the suns rays, just beyond the earths atmosphere at the average earth-sun distance) is 1367 W/m2.大气层外太阳辐射强度随日期的变化 Spectral Solar Irradiation99 的能量集中在在0.28m到 5.0m的波段之间。Direct solar radiationDiffuse solar radiationGlobal solar radiationGlobal solar radiation Direct solar radiation Diffuse solar radiationShorter wavelength High proportionLonger wavelength Temperature increaseGreenhouse effectFive Elements of Passive Solar Home DesignAperture (Collector) The large glass (window) area through which sunlight enters the building. Absorber The hard, darkened surface of the storage element. Thermal mass The materials that retain or store the heat produced by sunlight. Distribution The method by which solar heat circulates from the collection and storage points to different areas of the house. Control Roof overhangs can be used to shade the aperture area during summer months.Active solar heating system1: Sensor 传感器 2: Air Vent 排气口 3: Sensor wire 传感器线 4: Pump or circulator 循环泵 5: Pressure Relief Valve 减压阀 6: Sensor 传感器 7: Pressure Relief Valve 减压阀 8: Thermometer 温度计 9: Tempering Valve 混水阀 调温阀 10: Hot water output 热水输出 11: Cold water feed line 补水管 12: Knob adjusts water temperature output 13: Bypass “H” valve 旁通阀 14: Check Valve 逆止阀 15: Solar collectors inlet 太阳能采集器入口 16: Pressure Relief Valve 减压阀 17: Collectors 12. Factors such as cloud cover and geographical location affect the total amount of solar energy received. 14. This is possible because ordinary glass can transmit the shorter wavelength, visible parts of the sunlight while at the same time preventing the passage of the longer wavelength, invisible heat waves.separate from: 除过 greenhouse: 温室ordinary: 普通的 transmit: 传播 传递 passage: 通过 shorter wavelength: 短波 longer wavelength: 长波assemble: 组装装配 low concentration: 低密集度13. Separate from the more obvious uses of energy from the sun, such as drying food and warming people, the most common direct use of solar energy is in a greenhouse.15. To get the most from solar energy, a system must be assembled to collect the low concentration of solar energy efficiently and store the heat energy to use at night and on cloudy days.17. This data can be obtained from a pyronometer, a device that measures insolation (energy from the sun) in Btu per square foot per hour.proposed: 被提议的reading: 读数 carry away: 带走pyronometer: 日射强度计 insolation: 日射能量16. Designing a solar installation requires precise information on the amount of solar energy available at the proposed location.18. Heat flow readings can be compared to insolation data to show how efficiently the collector is operation; that is, how much of the available energy is being carried away by