Heating, Ventilation and Air Conditioning (HVAC) Laboratory
Laboratory equipment
The HVAC laboratory contains an Air conditioning unit, which is set up with all necessary heat and cold supply loops along with the humidification (with water and steam) and dehumidification equipments.
Up to an air volume flow rate of 2000 m³/h can be heated, cooled, humidified and dehumidified and supplied to the laboratory through different air outlets. The system consists of the following components: heater, cooler, cross-flow heat recovery heat exchanger, steam humidifier, spray humidifier, mixing chamber, backward-curved speed-regulated radial fan, belt-driven forward-curved radial fan, silencer, filters and comprehensive instrumentation and control facilities.
All components can be individually operated and their performance can be evaluated. The influence of different control concepts on the energy consumption and on the system’s behaviour and performance can be demonstrated, and individual control parameters can also be modified. All processes can be displayed with the help of a software in the Mollier-h-x-diagram.
The flow of supply air into the room through the different air outlets can be visualised by means of a mist generator. The airflow rate inside the AC unit can be measured by a Venture-meter coupled to the supply air fan and verified by measuring the air flow velocity and –rate inside the air ducts by means of modern pitot tubes, vane and a hot-wire anemometers.
Comfort sensors and a globe wet-bulb thermometer are used to carry out comfort measurements in terms of the effect of air temperature, relative humidity, air speed (wind chill) as well as visible and infrared radiation (usually sunlight) on humans.
A Carrier chiller utilizing R407C as a refrigerant having a maximum refrigerating capacity of 15.4 kW provides cold water for the cooler of the AC unit through a cold storage tank. The chiller can be energy balanced for experimental purposes. The measured data can be presented in the log p-h diagram of the refrigerant to estimate among others, the isentropic efficiency of the compressor.
An electric heat storage boiler with a connected electrical heating rate of 24 kW and a storage capacity of 700 l for storage of PV-surplus electricity in heat is demonstrated to supply heat to the AC unit.
A gas condensing boiler is available for practical experiments. The amount of heat delivered is determined by different volumetric flow measurements (MID, rotameter and a gear meter) and temperature measurements. The gas volume flow rate is measured in order to estimate the condensing boiler efficiency.
The exhaust gas can be analysed by chimneysweep into a special waste gas meter, which is able to estimate the exhaust gas heat loss leading to estimating the condenser boiler efficiency based on the lower calorific value. Various boiler control functions like e.g. setting up the heating curve and selecting different operation modes can be demonstrated and tested.
The laboratory contains a highly innovative Viessmann-Panasonic fuel cell hybrid heating appliance, which comprises the following two heating systems:
- A fuel cell module with an electrical rated power of 0.75 kWel and a heat output von 1 kWth, sufficient to cover the base load of a detached single-family houses, and
- A peak load gas condensing boiler with a rated heat output of up to 20 kWth.
The system also includes a hot water storage tank and a domestic hot water tank plus all necessary sensors, actuators and control units. The test rig is equipped with the instrumentation needed to be able to fully energy balance the fuel cell heater and or the condensing boiler.
The hybrid gas heating appliance incorporating the Fuel cell and the peak condensing boiler
Hydraulic test rig
This compact test rig allows students to perform all of the operations necessary to hydraulically set up and test a heating system, e.g. hydraulic balancing, pump circuits, venting, differential pressure valves, setting up thermostat valves, measuring flow resistances etc.
Thermographic camera
The laboratory infrared cameras are applied to view thermographic images of the temperature distribution inside buildings and technical facilities such as underfloor heating systems, allowing the early detection of any defects that may be present. In addition, having thermographic pictures of external building facades allow the analysis the existence of thermal bridges or even water leakage on those facades.
A test rig is used to demonstrate how a heat-recovery ventilation system operates. Fresh outside air flows to domestic living spaces across a central unit with heat recovery, filters, blowers and heater coils. The waste air is extracted from the WC and kitchen and blown outside by the central unit.
Heat-recovery ventilation provides the building with the necessary flow of fresh air to ensure comfortable air conditions and offers the enhancement of the energy utilization efficiency through internal heat recovery in winter and summer operations. Allergy sufferers in particular will appreciate the filtered pollen-free fresh air. HRV can also counteract the formation of mould caused by the modern airtight double-glazed or triple-glazed windows and the inadequate ventilation.
A Wolf brine/water heat pump with a 10 kW rated heat capacity is set up on a dedicated test rig in the laboratory. The volume flow rates of brine and heating water along with feed and return temperatures in both loops are continuously measured.
The laboratory includes also a blower door test facility for measuring the airtightness of buildings. A suitable measurement tent is also available for student practical trainings.
The blower door test comprises an impermeable nylon liner that is stretched in an airtight manner into an opening in the building by means of an adjustable frame. The blower is then mounted in an opening in the liner and held in position by a heavy-duty elastic strap. Once installed, the electric blower is activated and depending on which way round it is installed, it blows air out of or into the building under test, so lowering or raising the pressure inside.
The objective of this exercise is to create a differential pressure of 50 Pa between the inside and the outside and then measure the volume airflow entering or leaving the building through leaks and openings. The volume flow through leaks in the building’s envelope (through the leaks) is equal to the volumetric flow generated by the blower.
The volumetric flow through the blower can be measured with a connected portable meter or computer software and used to determine the building’s air change rate, which can then be compared and graded by reference to limits specified in national or international standards.
The following solar thermal collectors are installed on the collector test rig:
- Flat plate collector
- CPC vacuum tube collector
- Heat pipe vacuum tube collector
These collectors are incorporated in a test rig configured to simulate a solar water heating installation in a detached house. The thermal output of each collector can be measured.
Artificial sunlight is provided by a special mobile floodlight truck carrying 3 large floodlights of 2000 W each projecting a sun-like spectrum. The truck also carries 18 halogen headlights of 400 W each, which also produce sun-simulating daylight. Suitable pyranometers are used to measure the intensity of the radiation on the collectors so that their efficiency can be determined and compared with the manufacturer’s data.
Solar collector test rig with the comprehensive measuring and control facilities and the Laboratory Solar Simulator
This test array allows the investigation of the different losses of a solar collector. The array comprises nine small collectors all with different absorber panels, glass covers and types of insulation; a small vacuum tube based on the heat pipe principle is also included. These test collectors are irradiated with a floodlight and the temperature of the individual collectors is measured. Depending on the quality of the insulation and the collector’s transmittancy and absorptivity, a different stagnation temperature is obtained and its time span curve can be plotted and visualised on a PC.
- The radiation is absorbed and emitted at different strengths depending on the type of absorber plate and/or its coating.
- Without a glass cover, the heat can be immediately lost to the environment through convection.
- Using window glass as a cover prevents heat loss through convection to the environment, however window glass also has a low transmission factor, so not all of the radiation reaches the absorber plate.
- A cover made from low-iron glass has a higher light transmission than window glass.
- Insulating the back of the absorber plate prevents convective heat loss to the rear side of the collector.
The approximate efficiency can be determined on the basis of the achieved stagnation temperature and the measured radiation.
Two PV modules – one fault-free and one faulty – are irradiated with halogen floods. The current, voltage and output ´power of the two modules can be measured for different external loads (filament bulbs). In this way, their characteristics can be plotted and the performance of the two modules can be compared to each other. The PV test rig can also be applied to demonstrate the dramatic effect of the partial shading of individual cells. The hotspots of the faulty module can also be detected with the use of a thermographic camera.
A professional HT I-V400 multifunction instrument is also available for testing and measuring PV systems. The measurement results can be compared with the manufacturer’s data to identify any deviation from the guaranteed performance.
Software
A wide variety of programs are installed on different workstation PCs in the laboratory. These include:
Energy Consultant “Energieberater”: For balancing buildings, investigating different upgrade options and creating energy performance certificates.
Polysun: Provides detailed simulation of a complete year of complex networked systems such as heat pumps and pellet boilers with thermal solar systems and seasonal thermal storage, photovoltaics and wind farms for supplying buildings with energy.
mh-Software: For calculating U-values as well as heating and cooling loads.
COMSOL-Multiphysics with the heat transfer module: For steady state and dynamic modelling of heat and mass transfer components.
gPROMS Model and Process Builder: For steady state and dynamic modelling, parameter estimation and optimization of energy systems.
Research and teaching
The test facilities listed in this overview are an integral part of the teaching process in the framework of different practical training courses.
In addition, we continuously offer several student projects, bachelor-, master- and Ph.D.- research studies to make use of the excellent infra structure available also in cooperation with external industrial companies.