arne22
09-03-2011, 02:43 PM
Hello !
I/we are doing a inverter control system for a full scale laboratory heat pump that shall/will be inverter controlled. From asking a few qustion in this forum before, I got some information and hints to find even more information.
The advice was among other to search and to find some info about existing commersial heat pumps. So I did, and the information on the Daikin heatpump was quite good and informative. Link (http://www.daikinac.com/commercial/docsOverview.asp?sec=docs)
What I have found out is that Daikin uses a PI regulator + an inverter to set the speed of the comressor and that there is also some other means of setting the spead of the evaporater/condenser as well. (But more using mure simle solutions like using steps like low-medium-high rateher than PI or PID control.)
The Daikin dokumentation referes to the condenser temperature as the feed-back signal for the comressor speed controller.
In some way this sounds reasonable as what comes out of the condenser is heat.
On the other hand what the compressor makes is not (in the first place) heat, but rather "pressure", and then as a consequense of that, it comes also temperature. If you messure the temperature at the outher surface there should (teroretically) be a time delay between the change in pressure and change in temperature, at least if measured at the outside of the condenser. (If it is measured at the outside.)
One thing I wonder about: Why don't they rather measure the pressure inside the condenser and use this signal as the feedback to to the compressor speed loop ?
(Should't this give a shorter time constant and a more presice compressor control ?)
One other "hidden" or related question: What is the standard relation between temerature and pressure in a condenser, using a standard referigation media ? (R135A or other)
If temperature goes up "a little" lets say from 45 to 50 degres Celsius (if this is reasonable values), what will then happen with temperature, will it rise a lot more or a lot less, or is it possible to say anything about that ?
Could it be some certain reason why Daikin uses condenser temperature and not condenser pressure as the feed-back to the compressor control loop ?
Anyone with some interesting ideas about this ?
Excuse me for posting "to much" about the same subject, but it actually helps, and I think we are now rather close to find out how to do it. Feed back from this forum and the Daikin dokumentation actually helped quite well.
Best reg Arne.
I/we are doing a inverter control system for a full scale laboratory heat pump that shall/will be inverter controlled. From asking a few qustion in this forum before, I got some information and hints to find even more information.
The advice was among other to search and to find some info about existing commersial heat pumps. So I did, and the information on the Daikin heatpump was quite good and informative. Link (http://www.daikinac.com/commercial/docsOverview.asp?sec=docs)
What I have found out is that Daikin uses a PI regulator + an inverter to set the speed of the comressor and that there is also some other means of setting the spead of the evaporater/condenser as well. (But more using mure simle solutions like using steps like low-medium-high rateher than PI or PID control.)
The Daikin dokumentation referes to the condenser temperature as the feed-back signal for the comressor speed controller.
In some way this sounds reasonable as what comes out of the condenser is heat.
On the other hand what the compressor makes is not (in the first place) heat, but rather "pressure", and then as a consequense of that, it comes also temperature. If you messure the temperature at the outher surface there should (teroretically) be a time delay between the change in pressure and change in temperature, at least if measured at the outside of the condenser. (If it is measured at the outside.)
One thing I wonder about: Why don't they rather measure the pressure inside the condenser and use this signal as the feedback to to the compressor speed loop ?
(Should't this give a shorter time constant and a more presice compressor control ?)
One other "hidden" or related question: What is the standard relation between temerature and pressure in a condenser, using a standard referigation media ? (R135A or other)
If temperature goes up "a little" lets say from 45 to 50 degres Celsius (if this is reasonable values), what will then happen with temperature, will it rise a lot more or a lot less, or is it possible to say anything about that ?
Could it be some certain reason why Daikin uses condenser temperature and not condenser pressure as the feed-back to the compressor control loop ?
Anyone with some interesting ideas about this ?
Excuse me for posting "to much" about the same subject, but it actually helps, and I think we are now rather close to find out how to do it. Feed back from this forum and the Daikin dokumentation actually helped quite well.
Best reg Arne.