Final control questions on the subject “heat engineering” The purpose and function of the subject. Working parameter. Status parameters. Base words and phrases

 
Base words and phrases: flat wall, scheme, temperature, amount of heat, flow 
A transfer of heat from one medium (liquid or gas) to another medium 
heat transfer through a layered or multi-layered solid wall 
is called 
Heat of a single-layer wall with a thickness of 8 and a surface area of 1 m2 
conductivity coefficient X (W/mK), ambient temperatures tsl and ts2 and 
heat transfer coefficients a, and a 2 of both sides are given (59- 
picture). Heat passes from the warm environment to the wall by convection: 

---

heat passes through the wall by conduction: 
passes from the wall to the environment by convection: 
q = a 2 (t.,, - U 
Expressing these expressions in terms of temperature difference, then adding heat 
we form the transfer equation: 
where k is the heat transfer coefficient. 
The heat transfer coefficient is numerically a unit within a unit of time 
to the amount of heat transferred when the temperature difference on the surface is equal to 1°C 
equal to Heat is the inverse of the heat transfer coefficient 
is called complete thermal resistance of transmission 
Heat flux density passing through a multilayer flat wall 
(for example, a three-layer wall): 
here: 
Heat flux Q through a flat wall with surface area F (m2). 
equal to 
Q = q • F = £ • At • F W (261) 
The temperatures between the wall layers are found as follows 
The temperature between the layers is found by the 
following formulas: 

---

23. Thermal conductivity through a single-layer cylindrical wall. 
 
Base words and phrases: temperature, scheme, amount of heat, cylinder, layer, formula 
Logarithmic curve of temperature at the cylindrical wall under conditions where x=const 
varies linearly and is expressed by the following equation. 
Passing through a single-layer cylindrical wall of length C 
the amount of heat is determined by the following expression 
The heat flux density is given per unit internal surface of the cylindrical wall 
it can: 
and to the external surface unit: 
and along the length of the pipe: (linear density of heat flow) 
The thermal conductivity through a single-layer cylindrical wall describes the ability of heat to 
flow through a cylindrical wall made of a single material. Here are some base words and 
phrases related to thermal conductivity through a single-layer cylindrical wall: 
- Temperature: The thermal conductivity through a single-layer cylindrical wall depends on the 
temperature difference between the inside and outside of the wall. The greater the temperature 
difference, the higher the rate of heat transfer through the wall. 
- Scheme: The thermal conductivity through a single-layer cylindrical wall can be represented by 
a schematic diagram that shows the layer of the wall and the direction of heat flow through it. 

---

- Amount of heat: The amount of heat that is transferred through a single-layer cylindrical wall is 
proportional to the thermal conductivity of the material it is made of, the temperature 
difference across the wall, and the surface area of the cylinder. 
- Cylinder: A cylinder is a shape that is common in pipes and tubes, and can be used as a model 
for thermal conductivity studies. 
- Layer: The single-layer of cylindrical wall refers to the layer of material that makes up the wall. 
The thermal conductivity of the material is an important factor in determining the rate of heat 
transfer through the wall. 
- Formula: The formula used to calculate the heat transfer rate through a single-layer cylindrical 
wall is given by Fourier"s law, which states that the heat flow rate is proportional to the 
temperature difference and the thermal conductivity of the material divided by the thickness 
of the wall. 
In summary, the thermal conductivity through a single-layer cylindrical wall is a measure of its 
ability to conduct heat through it. The temperature difference between the inside and outside 
of the cylinder, its surface area, and the thermal conductivity of the material are all factors 
that determine the rate of heat transfer through the cylinder. Fourier"s law is used to calculate 
the rate of heat transfer, taking into account the thickness of the material. 
24. Thermal conductivity through a multilayer cylindrical wall.