Vibrationsdämpning av värmepump

Sammanfattning

Thermia Värme AB is one of the market leading manufactures of heat pumps. In order to

maintain this position, the company wants to improve the vibration characteristics of their

products. The aim of this thesis is to develop product design changes that lead to a reduction

of vibrations in the heat pump Thermia Diplomat 8.

The main cause for vibrations in the system is flow pulsation and mechanical forces induced

by the scroll compressor. Vibration is transmitted through the compressor piping and received

by the heat exchangers, from where it is further transmitted to the connection points for the

radiator and heat source circuits.

A number of design changes in order to improve the vibration characteristics have been

evaluated through calculations and practical experiments. The changes have included the

compressor and heat exchanger mountings, the compressor suction and discharge line piping

and also pulsation dampening.

The results of the experiments show that the vibration levels in the connections for the heating

and brine circuits can be decreased strikingly through changes in suction and discharge line

piping. Further improvements concerning the vibration levels in both the heating and brine

connections and the framework of the heat pump are achieved through detaching the heat

exchanger mountings from the compressor mounting plate.

Furthermore, a number of proposals to additional improvements of the system have been

lightly described. These suggestions include modification of the heating and brine circuit

piping. Significant improvements are considered to be achieved through using the big mass

inertia of the hot water tank as an isolating element for the piping connections. Also a

replacement of copper tubes that have unwanted natural frequencies with shorter pipe lengths

or flexible hoses would decrease the vibration transmission.