The selection of electric heating tube needs to consider the power
The calculation of the power of the electric heating tube can be easily carried out in the following three steps through standardized and unified calculation:
1. Calculate the power required to maintain the temperature under the premise of maintaining the medium temperature unchanged
2. Calculate the power required to heat from the initial temperature to the set temperature within the specified time
3. Select the model and quantity of heater according to the above two calculation results. Take the maximum of the above two powers as the total power and consider the coefficient of 1.2.
1. Power required to maintain medium temperature pumping
Where: m3 added medium kg / h per hour
2. Power required for initial heating
KW = ( C1M1△T + C2M2△T )÷ 864/P + P/2
Where: C1C2 is the specific heat of container and medium (kcal / kg ℃)
M1m2 is the mass of container and medium respectively (kg)
△ t is the difference between the required temperature and the initial temperature (℃)
H is the time required for the initial temperature to reach the set temperature (H)
P heat dissipation of vessel at final temperature (kw)
The performance curve is often used in the calculation of electric heating pipe.
The selection of electric heating tube shall consider voltage:
The voltage specification of the electric heating tube must be confirmed before purchase. The confirmation of this step is equal to the fixation of the resistance value on the equipment. The higher the voltage is, the greater the power is. It is particularly easy to let the voltage exceed the load of the electric heating tube and lead to the fuse of the resistance wire of the generator, or even the breakdown of the electric heating tube. Normal voltage specification: 24V, 36V, 48V, 110V, 220V, 380V, generally we refer to the rated voltage.
Rated voltage of electric heating tube:
The rated voltage of the electric heating tube refers to the voltage connected to the electric heating tube specified in the redesign and marked on the shell of the electric heating tube. Or in other words, the rated voltage is the voltage that customers require us to give when we process and produce. Generally, there are 24V, 48V, 110V, 220V, 380V, etc.
Working voltage of electric heating tube:
(1) multiple series power supply: for a group of electric heating tubes or electric heating tubes connected in series to the power supply, the working voltage of the electric heating tube refers to the voltage specified in the design to be connected to this group of electric heating tubes.
(2) single connected power supply: for the electric heating tube with single connected power supply, the working voltage of the electric heating tube refers to the voltage on the element specified in the design, that is, the rated voltage.
Note: this involves the question whether multiple electric heating tubes are connected in series or in parallel. Therefore, when judging the voltage, if more than one electric heating tube needs to be connected, it is necessary to consider whether it is connected in series or in parallel, so as to determine the voltage of a single electric heating tube.
Effect of voltage on Power:
When the power of the electric heating tube is determined, if the voltage is less than the design voltage, the power will be reduced, and the heating efficiency will also be reduced; if the voltage is greater than the design voltage, the power will be increased, the load will be too high, and the internal electric heating wire may be blown, or even the electric heating tube will be broken down.
The selection of electric heating pipe needs to consider the pipe diameter:
When selecting the electric heating pipe, it is necessary to consider the matching between the pipe diameter and the hole diameter of the formwork. Because the pipe diameter is too large, the electric heating pipe cannot be installed into the hole position, the outlet end is not fixed, and the electric heating pipe moves. Therefore, it is necessary to consider that the pipe diameter cannot be too small, and the space between the too large pipe and the hole wall cannot be reserved, which affects the heat transfer effect of the electric heating pipe and the expansion of the pipe after heating and affects the service life.