The design of a building's windows significantly affects thermal energy transfer, primarily through conduction and radiation. Windows typically have a lower thermal resistance compared to walls, making them critical points for heat loss in winter and heat gain in summer. Double-glazing, where two panes of glass are separated by an air gap, reduces heat transfer by conduction and convection within the air gap. Low-emissivity (low-E) coatings on glass can reflect infrared radiation, minimising heat transfer without reducing visible light transmission. Argon or krypton gas fills between panes provide better insulation than air due to their lower thermal conductivity. These design features enhance energy efficiency by maintaining interior temperatures more effectively, reducing the reliance on heating and cooling systems, and consequently lowering energy consumption and costs. In regions with extreme temperatures, the impact on energy efficiency is particularly significant, making window design a key consideration in sustainable building practices.

Thermal energy transfer is fundamental to the operation of refrigerators and freezers, involving primarily conduction and convection processes. Inside a refrigerator or freezer, a refrigerant circulates through coils and undergoes a cycle of evaporation and condensation. During the evaporation process inside the coils, the refrigerant absorbs heat from the interior of the appliance, effectively removing heat from the stored items. This heat absorption occurs mainly through conduction as the inner surfaces of the fridge or freezer conduct heat to the refrigerant. The warm refrigerant then circulates to the coils at the back or bottom of the appliance, where it releases the absorbed heat into the external environment by condensation – a process enhanced by convection as air flows over the coils. This cycle repeats, maintaining the cold internal environment. Efficient thermal energy transfer in this system is crucial for the preservation of food and other perishable items, by keeping them at a consistently low temperature.

Thermal insulation in clothing works by trapping air within the fabric, utilising the poor conductive properties of air to reduce heat transfer. The effectiveness of insulation depends on the ability of the material to trap air in small pockets. Common materials used for thermal insulation in clothing include wool, fleece, and synthetic fibres like polyester. Wool fibres have a natural crimp, creating tiny air pockets that trap heat. Synthetic materials, often used in outdoor and performance clothing, consist of fine fibres woven into a dense network that traps air. These materials also have moisture-wicking properties, transporting sweat away from the skin, which is essential for maintaining warmth in cold environments. Down, which consists of the soft feathers found under the tougher exterior feathers of birds, is another effective insulator, trapping large volumes of air in a small space. The choice of insulating material depends on factors like warmth-to-weight ratio, water resistance, and breathability, with different materials suited to different climatic conditions and activities.

Car engines are designed with a keen focus on thermal energy transfer to ensure both efficiency and safety. The combustion process within an engine generates a significant amount of heat, which, if not properly managed, can lead to overheating and engine failure. To prevent this, car engines are equipped with cooling systems that use convection to transfer excess heat away from the engine. A coolant fluid circulates around the engine, absorbing heat through conduction. This hot coolant is then pumped through a radiator, where it loses heat to the surrounding air, again through convection. Additionally, the engine's metal components are designed to efficiently conduct heat to the coolant. For safety, engines also include thermal sensors and warning systems to alert the driver if the engine temperature exceeds safe limits. Advances in materials and design continue to improve the efficiency of these thermal management systems, enhancing engine performance and longevity.

Thermal energy transfer is crucial in the design of electronic devices like smartphones and laptops, primarily to prevent overheating, which can reduce performance and lifespan. These devices generate heat mainly due to electrical resistance and the operation of their internal components, like the CPU and GPU. Efficient heat dissipation is achieved through several means. First, the use of materials with high thermal conductivity, like aluminium or copper, in the device's body and internal structures facilitates the conduction of heat away from hot components. Secondly, heat sinks, often made of metal with a large surface area, are used to increase heat dissipation by convection. In more advanced designs, especially in laptops, heat pipes or even vapour chamber cooling systems are employed. These systems use the principles of phase change and convection to efficiently transfer heat away from the components. Additionally, thermal management software regulates the performance of the device to balance processing power with heat generation. The ongoing miniaturisation of components adds complexity to thermal management, making it a key focus in the design and innovation of personal electronic devices.