# 顕熱、潜熱、全熱

$$H_S = 1.08 \times CFM \times \Delta T$$

$$H_L = 0.68 \times CFM \times \Delta W_{GR}$$

$$H_T = H_S + H_L$$

どこ：

• HSは顕熱 (Btu/hr)
• HLは潜熱 (Btu/hr)
• HTは総熱量 (Btu/hr)
• CFM空気流量 (立方フィート/分)
• ΔTは温度差 (°F)
• ΔWGRは湿度比の差 (粒子 H2O/ポンド DA)

エアコンは部屋から 10,000 Btu/hr の総熱を除去します。 空気流量は 1000 CFM、温​​度差は 20°F です。 湿度比の差は 0.005 グレイン H2O/ポンドです。 DA。

$$H_S = 1.08 \times 1000 \times 20 = 21,600 Btu/hr$$

$$H_L = 0.68 \times 1000 \times 0.005 = 3.4 Btu/hr$$

$$H_T = H_S + H_L = 21,600 + 3.4 = 21,603.4 Btu/hr$$
コンテンツ

### U 値と面積

$$H = U \times A \times \Delta T$$

どこ：

• Hは熱伝達率 (Btu/hr)
• Uは U 値 (Btu/hr. ft². °F)
• 面積 (ft²)
• ΔTは温度差 (°F)

$$H = 0.25 \times 100 \times 20 = 500 Btu/hr$$

### 顕熱比 (SHR)

$$SHR = \frac{H_S}{H_T} = \frac{H_S}{H_S + H_L}$$

$$SHR = \frac{21,600}{21,603.4} = 0.999$$

What is the difference between sensible heat and latent heat in terms of temperature change?
Sensible heat is associated with a change in temperature of a substance, whereas latent heat is associated with a phase change of a substance without a change in temperature. For example, when water is heated from 20°C to 80°C, the heat added is sensible heat because the temperature of the water increases. However, when water is heated from 100°C to 110°C and it changes from a liquid to a gas, the heat added is latent heat because the temperature remains constant during the phase change.
How does the specific heat capacity of a substance affect sensible heat transfer?

The specific heat capacity of a substance determines how much heat energy is required to change its temperature by a given amount. Substances with high specific heat capacities, such as water, require more heat energy to change their temperature than substances with low specific heat capacities, such as air. Therefore, when designing HVAC systems, it’s essential to consider the specific heat capacity of the substances involved in heat transfer to ensure efficient sensible heat transfer.

What is an example of latent heat transfer in an HVAC system?

A common example of latent heat transfer in an HVAC system is the dehumidification process in an air conditioning system. When moist air passes over a cooling coil, the latent heat of vaporization is transferred from the air to the coil, causing the water vapor to condense into liquid water. This process reduces the humidity of the air and removes heat from the space, making it an essential component of air conditioning systems.

How is total heat calculated in an HVAC system?

Total heat is calculated by summing the sensible heat and latent heat transferred in an HVAC system. The sensible heat can be calculated using the specific heat capacity of the substance and the temperature change, while the latent heat can be calculated using the latent heat of vaporization or fusion and the mass of the substance undergoing a phase change. For example, in a cooling coil, the total heat transfer can be calculated by adding the sensible heat transfer due to the temperature change of the air and the latent heat transfer due to the condensation of water vapor.

What are the units of measurement for sensible, latent, and total heat?

The units of measurement for sensible, latent, and total heat are typically measured in joules (J) or British thermal units (BTU). The specific heat capacity of a substance is typically measured in joules per kilogram per kelvin (J/kg·K) or BTU per pound per degree Fahrenheit (BTU/lb·°F). The latent heat of vaporization or fusion is typically measured in joules per kilogram (J/kg) or BTU per pound (BTU/lb).

How does the humidity of the air affect latent heat transfer in an HVAC system?

The humidity of the air has a significant impact on latent heat transfer in an HVAC system. When the air is humid, there is more moisture available to condense on the cooling coil, resulting in a greater amount of latent heat transfer. Conversely, when the air is dry, there is less moisture available to condense, resulting in less latent heat transfer. Therefore, it’s essential to consider the humidity of the air when designing HVAC systems to ensure efficient latent heat transfer.

What are some common applications of total heat transfer in HVAC systems?

Total heat transfer is an essential concept in various HVAC applications, including air conditioning systems, heat pumps, and refrigeration systems. It’s used to calculate the total cooling or heating capacity of a system, which is critical for selecting the appropriate equipment size and designing efficient systems. Additionally, total heat transfer is used to analyze the performance of HVAC systems and identify opportunities for energy savings and optimization.