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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

Pergunta

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

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

Solução

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AdãoElite · Tutor por 8 anos

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To determine whether a cooling or heating system is required, we need to calculate the heat gain and heat loss of the building.<br /><br />First, let's calculate the heat gain from the external load:<br />Heat gain from external load = 2 kW<br /><br />Next, let's calculate the heat gain from the internal load:<br />Heat gain from internal load = 1.2 kW<br /><br />Now, let's calculate the heat loss through the building envelope using the U-value:<br />Heat loss through building envelope = U-value * exposed surface area * (external temperature - internal temperature)<br />Heat loss through building envelope = 0.5 W/m².K * 384 m² * (3°C - 25°C)<br />Heat loss through building envelope = 0.5 * 384 * (-22)<br />Heat loss through building envelope = -4224 W or -4.224 kW<br /><br />The total heat gain is the sum of the heat gain from the external load and the internal load:<br />Total heat gain = 2 kW + 1.2 kW = 3.2 kW<br /><br />The total heat loss is the absolute value of the heat loss through the building envelope:<br />Total heat loss = 4.224 kW<br /><br />Since 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.<br /><br />If the U-value of the building is 0.6 W/m².K, the heat loss through the building envelope would be:<br />Heat loss through building envelope = 0.6 W/m².K * 384 m² * (-22°C)<br />Heat loss through building envelope = -0.6 * 384 * (-22)<br />Heat loss through building envelope = -8358.4 W or -8.3584 kW<br /><br />In 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.
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