What is the thermal conductivity, heat transfer resistance and heat transfer coefficient?

The heat transfer coefficient used to be called total heat transfer coefficient. The current national standards and norms are uniformly named as heat transfer coefficient. The value of heat transfer coefficient k refers to the temperature difference between the air on both sides of the enclosure structure is 1 degree (k,℃) under the stable heat transfer condition, and the heat transferred through an area of 1 square meter in 1s is expressed in watts/(square meters per degree) (w/㎡ k, where k can be replaced by æ).