Design of air coil dehumidification

Abstract: Experiments in school are designed for students to study and learn about real life phenomena by using models. If the student are going to be able to learn as much as possible the model needs to simulate reality well. During the course MJ2407 at KTH there is an experiment where the students study heat transport via heat exchanger in air conditioning systems. In the current experimental setup the air gets heated by a heater and then cooled down by the heat exchanger; the air is circulating through a closed loop in this manner by a fan. To better simulate reality, where the air which is entering the air conditioner usually contains more moisture, it has been decided that a humidifier is to be installed. This report is about the work regarding installing that humidifier. A model for the new experimental setup was drawn up. During the work which followed this model was changed on a number of occasions where new problems and solutions appeared. The nozzle for water injection that was used in the system was for example able to work with low enough pressure that the pump system, which was originally planned, could be exchanged for only a valve and a pressure sensor. Sensors for the relative humidity was installed before and after the heat exchanger. After testing the new setup a number of water leaks were discovered due to the fact that large parts of the water were not integrating with the air or condensed along the walls and at the heat exchanger. The old system was built using air ducts and therefor, sowas the new additions. These air ductswas not sufficiently sealed in the joints and had to be sealedwith silicone. Several drains were also installed in positions along the setup wheremasses of water collected. After the sealing and the installation of the drains the system was tested using different settings.The result was a raise in the relative humidity of the air by a 30 percentage points. The relative humidity was also stable for an extended time which corresponds well to a real life scenario where the incoming air gets taken from the outside. For future work with the experimental setup the student manual for this experiment needs to rewritten. To rewrite the student manual was originally a part of this project but there was not enough time to do it within the given time frame. It would also be a good idea to add more humidity sensors to the same positions so as to then get the average value from them. The energy consumption could be reduced by reusing the outgoing cooling water from the compressor. This water could be used in a secondary heat exchanger which could heat up the water used for humidity.