| abstract |
The present invention relates to a heating apparatus comprising a plurality of heat-transfer tubes (21) for passing a heat-transfer fluid, said heating apparatus comprising a light guide (10) located above a heating section (20) The light guide 10 has optical characteristics such that the incident light can be guided in various directions according to the incident angle of the incident light. When the incident angle is low, for example, most of the incident light is transmitted to the heat- When the incident angle is high, for example, it is guided to the side of the heat-transfer tube 21 in the summer. |