Question
1. A building has a U-value of 0.5W/m^2.K and a total exposed surface area of 384m^2 The building is subjected to an external load (only sensible) of 2 kW and an internal load of 1.2 kW (sensible). If the required internal temperature is 25^circ C State whether a cooling system is required or a heating system is required when the external temperature is 3^circ C v How the results will change, if the U-value of the building is so/n
Solution
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Elite · Tutor por 8 anos
Resposta
To determine whether a cooling or heating system is required, we need to calculate the heat gain and heat loss of the building.First, let's calculate the heat gain from the external load:Heat gain from external load = 2 kWNext, let's calculate the heat gain from the internal load:Heat gain from internal load = 1.2 kWNow, let's calculate the heat loss through the building envelope using the U-value:Heat loss through building envelope = U-value * exposed surface area * (external temperature - internal temperature)Heat loss through building envelope = 0.5 W/m².K * 384 m² * (3°C - 25°C)Heat loss through building envelope = 0.5 * 384 * (-22)Heat loss through building envelope = -4224 W or -4.224 kWThe total heat gain is the sum of the heat gain from the external load and the internal load:Total heat gain = 2 kW + 1.2 kW = 3.2 kWThe total heat loss is the absolute value of the heat loss through the building envelope:Total heat loss = 4.224 kWSince the total heat gain (3.2 kW) is greater than the total heat loss (4.224 kW), a heating system is required to maintain the required internal temperature of 25°C.If the U-value of the building is 0.6 W/m².K, the heat loss through the building envelope would be:Heat loss through building envelope = 0.6 W/m².K * 384 m² * (-22°C)Heat loss through building envelope = -0.6 * 384 * (-22)Heat loss through building envelope = -8358.4 W or -8.3584 kWIn this case, the total heat gain (3.2 kW) is still greater than the total heat loss (-8.3584 kW), so a heating system is still required.