What is internal heat gain?

Short Answer:

Internal heat gain is the amount of heat generated inside a building or closed space due to internal sources such as people, lighting, electrical equipment, and machinery. This heat adds to the indoor temperature and affects the cooling requirement of the building. Internal heat gain plays a significant role in designing air-conditioning and ventilation systems.

It mainly comes from everyday activities like using computers, cooking, lighting, and running machines. The more internal heat gain, the higher the need for cooling to maintain comfort. Managing internal heat gain helps improve energy efficiency and indoor comfort.

Detailed Explanation :

Internal Heat Gain

Internal heat gain refers to the heat generated within an enclosed space from internal sources such as occupants, lights, equipment, and other devices. Unlike solar heat gain, which comes from the sun’s radiation, internal heat gain originates inside the building. This type of heat contributes to raising the internal temperature and increasing the load on cooling systems.

In mechanical and building engineering, understanding internal heat gain is very important for calculating the cooling load of air-conditioning systems. If the internal heat gain is high, the cooling system must work harder to remove excess heat and maintain comfortable indoor conditions. Therefore, engineers carefully estimate internal heat sources during the design of HVAC (Heating, Ventilation, and Air Conditioning) systems.

The main sources of internal heat gain are:

  1. Occupants: Human bodies release heat continuously through metabolism. The amount of heat depends on activity level, clothing, and number of people. For example, a person sitting in an office gives off less heat compared to someone doing physical work.
  2. Lighting: Electrical lights convert part of the electrical energy into visible light and the rest into heat. Especially in commercial buildings with many lights, the total heat released can be significant.
  3. Electrical and Electronic Equipment: Computers, printers, televisions, kitchen appliances, and motors produce heat during operation. In offices or industries, these devices can contribute a large portion of internal heat gain.
  4. Cooking and Industrial Processes: In kitchens, restaurants, and factories, stoves, ovens, and machines emit large amounts of heat into the surrounding air.
  5. Building Materials: Even furniture and walls can absorb and release heat depending on their thermal properties and room temperature.

Internal heat gain can be sensible or latent in nature.

  • Sensible heat gain is the heat that increases the air temperature without changing moisture content. It comes from lighting, machines, and conduction.
  • Latent heat gain involves the addition of moisture to the air, such as from human perspiration, cooking, or boiling water. It affects humidity levels and must also be controlled by the air-conditioning system.

Controlling internal heat gain is essential for maintaining comfort and reducing energy consumption. Several methods are used to minimize unnecessary heat buildup. One of the most effective ways is to use energy-efficient lighting systems like LED lights that emit less heat than traditional lamps. Turning off unused equipment and using automatic control systems also helps reduce unnecessary energy use.

Proper ventilation and insulation are also key to controlling internal heat. Ventilation allows fresh air to remove heat and moisture, while insulation reduces the transfer of heat between spaces. In industrial setups, heat recovery systems can capture waste heat and use it for other processes, reducing the total load on cooling systems.

When designing a building or HVAC system, engineers perform a detailed heat load calculation, which includes both internal and external sources of heat. The internal load depends on how the space is used, the number of occupants, and the type of equipment installed. By estimating these factors accurately, the air-conditioning system can be designed to provide optimal cooling without wasting energy.

In modern buildings, especially in offices and commercial areas, internal heat gain can be very high due to heavy use of electrical equipment and computers. If not managed properly, it can cause discomfort, overheating, and reduced air quality. Therefore, proper design, equipment selection, and maintenance are necessary to maintain comfort and energy efficiency.

Example:

In a computer lab or office building with many computers and lights, a large amount of heat is generated even without sunlight. The air-conditioning system must remove this internal heat to maintain a comfortable temperature. However, if energy-efficient devices and lighting are used, the internal heat gain can be reduced, saving energy and cost.

Conclusion:

Internal heat gain is the heat produced within a space from people, lights, and equipment. It directly affects indoor temperature and the performance of cooling systems. By reducing unnecessary heat sources and using efficient devices, internal heat gain can be managed effectively. Proper control of internal heat gain ensures comfort, saves energy, and improves the overall performance of buildings and industrial spaces.