The heat transfer calculation formulas are: the law of heat conduction: q = -kA(dT/dx), where q denotes the amount of heat that passes through the object per unit of time, k is the thermal conductivity, A is the area of heat conduction, and dT/dx is the temperature gradient; and the formula for calculating heat transfer efficiency: η = (Q_out / Q_in) × 100%, where η denotes the efficiency of heat transfer, Q_out denotes the energy output, and Q_in is the energy input.
I. Heat transfer
Heat transfer is the transfer of energy due to temperature difference, also known as heat transfer. By the second law of thermodynamics can be seen, where there is a temperature difference exists, the heat will inevitably be transferred from the high temperature to the low temperature, so the heat transfer is the natural world and the field of engineering and technology is very common in a transfer phenomenon.
Whether in the energy, aerospace, chemical, power, metallurgy, machinery, construction and other industrial sectors, or in agriculture, environmental protection and other sectors are involved in many issues related to heat transfer.
Second, heat conduction
Heat conduction, refers to the material in the absence of relative displacement, the object has a different temperature, or different temperatures of the object in direct contact with the heat transfer phenomenon that occurs. Heat conduction in solids is derived from atomic activity in the form of lattice vibrations. In nonconductors, energy transfer occurs only by lattice waves (phonons); in conductors, in addition to lattice waves there is the translational motion of free electrons.
The higher the temperature, the greater the energy of the molecules, which means the greater the energy of the vibrations. When neighboring molecules collide, energy is transferred from the higher energy molecule to the lower energy molecule. Thereby, when there is a temperature gradient, energy transfer through thermal conductivity always takes place in the direction of lower temperature.
Effects of heat transfer
1. In the field of energy and environment
Heat transfer methods such as heat conduction and heat radiation determine the efficiency of heat transfer, which in turn affects the efficiency of energy utilization. For example, optimizing the thermal conductivity of building materials can improve a building's thermal insulation or insulation performance and reduce energy consumption.
2. Electronic equipment
Thermal conduction and thermal convection affect the operational efficiency and lifespan of equipment, so thermal design is critical.
3, in the biomedical field
The maintenance of normal body temperature, medical heat and cold therapy, and medical equipment such as high temperature steam sterilization are involved in heat transfer.