A building has an effective heat conductance – UA of 0.78 kW °Cí1 . From Monday to Friday, it is occupied for 14 hours from 7h to 20h, and unoccupied during the rest of the day. The building is...

A building has an effective heat conductance – UA of 0.78 kW °Cí1 . From Monday to Friday, it is occupied for 14 hours from 7h to 20h, and unoccupied during the rest of the day. The building is unoccupied during Saturday and Sunday. The rates of internal heat gain during the occupied and unoccupied periods are 3.2 kW and 1.1 kW respectively. The corresponding indoor temperatures are 21°C and 16°C respectively. The building is heated using a fuel-fired furnace of capacity 30 kW and rated efficiency 88%. The part-load degradation factor is 0.25. The bin data for three hour-groups for the location are given in Table E13.13.1. Calculate (i) the balance temperatures for the occupied and unoccupied periods, and (ii) the annual energy input to the furnace during the occupied and unoccupied periods.