Aiming at computing the heat transfer through multi-layer covering in environmental control design and insulation performance evaluation of a greenhouse, a computing method for thermal transmittance of multi-layer covering was developed based on the data of a single screen. According to heat transfer theory, the formula for saving ratio of heat loss of multi-layer screens were established from that of a single screen, and then the method for calculating the thermal transmittance of multi-layer covering was developed. The computing formula which quantifies the relationship between the heat transfer parameters of multi-layer covering and a single screen become simple by using a new parameter-heat insulation ratio. The high accuracy of the computing formula has been synthetically texted by different kinds of data. In a same case, the saving ratio of heat loss of three-layer screens established from that of a single screen was only 4.6% different from the same saving ratio of heat loss. The computing method developed in this paper can be used to calculate the saving ratio of heat loss and thermal transmittance for multi-layer covering, and avoid measuring the parameters of different multi-layer covering consisting of kinds of materials seriatim.%针对温室环境工程设计和保温性评价中多层覆盖传热计算问题,研究了根据单层保温幕保温性数据确定多层覆盖传热系数的方法.运用工程传热学理论,推导了由单层保温幕热节省率计算多层保温幕热节省率的公式,进而可计算多层覆盖传热系数.计算式揭示了温室单层保温幕和多层覆盖传热参数间的定量关系,通过引入传热阻比这一新概念,形式更加简明.采用多种数据的综合检验结果表明,所提出计算式准确性较高,同一情况下由单层保温幕热节省率计算得出的3层保温幕热节省率,与直接获得的同一热节省率最大相差仪4.6％.论文提出的计算方法,可避免对多种材料组合的各种多层覆盖进行逐一测试,系统地解决了多层覆盖传热计算中热节省率和传热系数确定的问题.
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