## Lab Station: Air Heater
## Description of the system
Figure 1 shows an air
tube with heater and temperature sensor(s). University College of Southeast
Norway, Porsgrunn, has 26 copies of this lab station, being used in several
control courses in both bachelor and master programmes in technology.
## Video presenting the air heater
## Mathematical model
A mathematical model that
has proven to describe quite well the dynamic behaviour of the outlet
air temperature (where one of the temperature sensors are mounted) in
simulations is as follows: T where ·
T ·
T ·
T theta where ·
u [V] is the control signal to the heater. ·
theta ·
K ·
theta In a simulator based on
this model a proper initial value of the state variable T The parameter values vary
somewhat between the lab stations. However, the following values are typical and
can be used (e.g. in a simulator) unless you have found other values from
experiments: ·
K ·
theta ·
theta Furthermore,
you may assume - T
_{env }= 20 deg C
## Experimental data
airheater_logfile.txt contains data from an experiment on the air
heater. (The fan speed was kept constant during the experiment.) The file containes three colums of data: - Time, t [s]
- Control signal to the heater, u [V]
- Outlet temperature, T_out [C].
## Technical information
Each air heater consists
of the following items: 1.
One plywood plate on which the devices are mounted 2.
Plastic box containing all electrical devices 3. One plastic tube 4.
One air fan (originally a PC fan) 5.
One potensiomter (variable resistance) for manual adjustment of the
voltage controlling the fan speed. 6.
One electric power cable (for connection to mains outlet, e.g. 220 V) 7.
Two temperature sensors, type Pt100, with measurement signal converter
from resistance to current: INOR miniPack-L 8. One heating element (coil) for electric heating of air. The coil is originally used in a shoe dryer. Power (assuming 220 VAC) is 250 W. 9. One electrical AC-DC converter from 220 VAC to 24 VDC. Datasheet_power_supply.pdf 10. One Pulse-width modulator (PWM): Carlo Gavazzi RN F23V30. Datasheet_ssr_pwm.pdf ## Publication
·
F. Haugen, Fjelddalen E, Edgar T., Dunia R., Updated 18 March 2018 by Finn Aakre Haugen. E-mail Finn.Haugen@usn.no. |