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一般认为,与普通蒸气养护相比较,热空气养护需要较多的热能,而且会降低混凝土的强度。但是在一些国家,如苏联、捷克、西德等,在隧道窑中都有采用这种方法的。计算表明(表1),采用热空气养护板型构件,其平均热能消耗比其他热养护方法稍大一些。大多数湿热养护方法的热利用率为30～40%,而且传导给混凝土的热量并不直接地与达到的强度有关。相对湿度低的热空气的内能低于饱和水蒸气。为了克服这一缺点,往往采取一些特别的工艺措施,如热空气循环、洒水等等。图1所示是热空气在不同的相对湿度和温差[K]下的传热系数的近似值α[瓦特/米~2、K]。
It is generally believed that hot air curing requires more thermal energy than conventional steam curing and will reduce the strength of the concrete. However, in some countries, such as the Soviet Union, Czech Republic, West Germany, etc., this method has been adopted in the tunnel kiln. The calculations show (Table 1) that the use of hot air for curing plate-type components has a slightly larger average heat consumption than other methods of heat conservation. The thermal efficiency of most heat and heat curing methods is 30 to 40%, and the heat conducted to the concrete is not directly related to the strength achieved. The internal energy of hot air with low relative humidity is lower than saturated water vapor. In order to overcome this shortcoming, some special technological measures are often taken, such as hot air circulation, watering, and the like. Figure 1 shows the approximate value α [W/M2, K] of the heat transfer coefficient of hot air at different relative humidity and temperature difference [K].