Abstract
A model for an HVAC system is derived in this
paper. The HVAC system consists of a room and a hydronic
radiator with temperature regulating valve (TRV) which has
a step motor to adjust the valve opening. The heating system
and the room are simulated as a unit entity for thermal
analysis and controller design. A discrete-element model
with interconnected small scaled elements is proposed for
the radiator. This models the radiator more precisely than
that of a lumped model in terms of transfer delay and
radiator gain. This precise modeling gives us an intuition
into a regular unwanted phenomenon which occurs in low
demand situations. When flow is very low in radiator and the
supply water temperature and the pressure drop across the
valve is constant, oscillation in room temperature occurs.
One reason could be the large gain of radiator in low
demand conditions compared to the high demand situations.
The simulation model of radiator is optimized in terms of
approximating the small signal gain of radiator in all
operating points accurately. The controller designed for high
demand weather conditions is applied to the opposite
conditions to illustrate the oscillatory condition more
apparently. Suggestions to alleviate this situation are
proposed.
paper. The HVAC system consists of a room and a hydronic
radiator with temperature regulating valve (TRV) which has
a step motor to adjust the valve opening. The heating system
and the room are simulated as a unit entity for thermal
analysis and controller design. A discrete-element model
with interconnected small scaled elements is proposed for
the radiator. This models the radiator more precisely than
that of a lumped model in terms of transfer delay and
radiator gain. This precise modeling gives us an intuition
into a regular unwanted phenomenon which occurs in low
demand situations. When flow is very low in radiator and the
supply water temperature and the pressure drop across the
valve is constant, oscillation in room temperature occurs.
One reason could be the large gain of radiator in low
demand conditions compared to the high demand situations.
The simulation model of radiator is optimized in terms of
approximating the small signal gain of radiator in all
operating points accurately. The controller designed for high
demand weather conditions is applied to the opposite
conditions to illustrate the oscillatory condition more
apparently. Suggestions to alleviate this situation are
proposed.
| Original language | English |
|---|---|
| Title of host publication | Proceedings of the 6th annual IEEE Conference on Automation Science and Engineering, Toronto, Ontario, Canada, August 2010 |
| Publisher | IEEE Press |
| Publication date | 21 Oct 2010 |
| ISBN (Print) | 978-1-4244-5447-1 |
| DOIs | |
| Publication status | Published - 21 Oct 2010 |