Bachelor's thesis Jannis Schumann

 

Assessment of psychromatic chamber and emergency ventilation concepts for hardware-in-the-loop test beds for heat pumps with flamable refrigerants

Front view of the overall concept consisting of climatic chamber, component test bench and exhaust air duct network. Copyright: EBC Front view of the overall concept consisting of climatic chamber, component test bench and exhaust air duct network.

By using air to water heat pumps (AWHP) to provide space heating, the primary energy consump-
tion in the building sector can be reduced. In contrast to the use of fossil fuels, e. g. in gas boilers,
heat pumps draw their energy from ambient heat and electricity. With increasing efficiency, the
consumption of electrical power is reduced. This leads to a reduction in primary energy consump-
tion.

A large proportion of the currently employed heat pumps use conventional refrigerants such as R-
134a and R-410A. These refrigerants have a high global warming potential, which is why a gradual
decrease of sales quantities has been laid down in the F-gas Regulation. If the demand for refrig-
erants remains constant or increases, this shortage will lead to price increases on the market. This
results in a need for alternative refrigerants to ensure the cost-effectiveness of heat pumps. One
example of such alternatives is propane. Propane has favourable thermodynamic properties for
use in compression heat pumps. However, safety precautions are necessary for testing propane
heat pumps, as propane is highly flammable.

One way to investigate heat pumps is in field tests. However, these are time-consuming, cost-
intensive and dependent on local weather conditions as well as consumer systems. Furthermore,
it is not possible to assess the impact of all disturbance variables. This is due to possible occur-
rences of design and installation errors as well as dynamic interactions between heat pump, heat-
ing system, user and weather conditions of varying degrees at any location. Two hardware-in-the-
loop (HiL) test benches are used at the Institute for Energy Efficient Buildings and Indoor Climate
(EBC) of the E.ON Energy Research Center (ERC). They are used to be able to include these inter-
actions in investigations and to minimise the effects of unknown disturbance variables. The water
circuit of the heat pump is connected to a hydraulic system which emulates individual building
behaviour. In addition, the outdoor unit of the AWHP is installed in a climatic chamber, which
emulates the temperature and humidity at the installation site with the aid of an air condition-
ing system. This method makes it possible to perform repeatable measurements under controlled
and observable conditions and at the same time take dynamic effects into account. The existing
HiL test stands HiL 1 and 2 are designed for conventional AWHP with a thermal output of up to
50 kW [1]. The existing test benches are not designed for tests on heat pumps with flammable
refrigerants.

This thesis deals with the design of a climatic chamber that meets the requirements for installa-
tion sites of propane heat pumps. In a first step, weather data of major German cities are examined
and the operating limits of the climate chamber regarding temperature and humidity are derived.
The dimensioning of the air conditioning section of the climatic chamber is based on a maximum thermal heating capacity of the test objects of 25 kW. A control system for the air conditioning system is developed in order to be able to emulate time-varying temperature and humidity profiles. A previously designed security concept is implemented. Finally, the concept of the designed climate chamber is evaluated.

This work extends the existing concept of HiL 1 and 2 test benches by implementing a safety con-
cept, which makes investigations on heat pumps with flammable refrigerants possible.