HEAT PUMPS
expenditure and achieving low operating cost of a building. European legislation has been developed in parallel as VRF application expands and efficiency demands drive the rate of progression further and further. There are however, limitations. Capacities of modular VRF systems are generally limited at approximately 230kW and their respective modular footprints, when using multiple systems, begin to get quite large when available plant space seems to be reducing. The amount of refrigerant circulating around a building can become high and the design hurdles to overcome potential refrigerant concentration legislation, if leakage occurs, can become quite expensive. This means that large building load demands generally require alternative solutions. The chiller market has developed highly efficient alternative solutions, lending themselves to the demands of modern building design, especially with recent restrictions through Ecodesign on minimum seasonal efficiency ratings. Adapting and utilising the technological developments that have taken place in the air conditioning sector, along with the variations in VRF application, means that chiller products have evolved.
This has taken what was once a predominately cooling-only product to a multi-functional mid to large capacity competitor.
The developments and comparative operational data driven by the Ecodesign directive and the F-GAS reduction process have made it easier for designers to change their habits. According to Eurovent Market Intelligence, 50kW to 350 kW capacity chillers make up two thirds of a £103 million market, with 90% of all chiller applications being air-cooled models. It is when we recognise the
aforementioned VRF limitations and look at the application potential of modern chillers, we can see why this market is growing. With a range of 49kW to 1.1mW; four pipe, heat pump, air cooled chillers allow dynamic design potential for providing both cooling and heating operations simultaneously. They are equipped to satisfy the various demands of today’s modern buildings. We recognise a chiller operating in a single mode as moving energy from one area and expelling in another. Chilled water being a product of the evaporator in cooling and hot water via the
Four pipe chiller producing chilled water and rejecting energy via the condenser fan to atmosphere.
condenser in heating. Generally, this energy would not be reusable and in turn lost to ambient air by the fan contained within the chiller’s chassis; acting to move air across the heat exchanger. When operating simultaneously, hot water can be generated utilising the heat rejected from the condenser and chilled water can be provided from the energy absorbed by the evaporator at the same time. The fan moving air across the heat exchanger is stopped and energy is transferred between the two heat exchangers, maintaining the refrigeration cycle’s operating pressures. This method not only provides a purpose to serve mixed applications, but also improves the system efficiency. What would normally be ‘lost’ energy is reused.
Simultaneous operation can create a system Total Energy Ratio (TER) of 8.8. That being 8.8kW of useful energy given out in terms of both heating and cooling in ratio to every 1kW of electrical energy consumed. These high efficiencies are not solely realised just from the concept of four pipe simultaneous systems, but also from the development of load control through both scroll and screw compressor innovation, inverter application and more complex control algorithms.
We can make comparisons here with the simultaneous operation of a heat recovery VRF system, but unlike VRF there are no heat
recovery boxes to install in the refrigerant pipework within the building. By using a third heat exchanger, either within the chiller or placed within a thermal store, energy to produce domestic hot water can also be utilised. This adds an efficient bivalent source to a traditional boiler or removing the need for a boiler altogether. The applications lending themselves to simultaneous operation are residential and commercial comfort cooling and heating through four pipe fan coils or underfloor heating methods. Domestic hot water use for hotels, leisure centres and spas. Data centre cooling whilst providing heating and DHW to staff offices, or more industrial uses in which chilled or hot water is required simultaneously in various forms through a process.
This modern way of thinking for energy recovery and multiple use products has given the chiller market the push it needed to bring it back in line with the extensive VRF possibilities, especially within the commercial market. With changes in using alternative low global warming potential refrigerants such as R452B, R513A and the ultra-low R1234ze, we now have products available to meet specification and regulation across an extensive array of capacities. This helps in negating the legislation
or avoiding pitfalls that become more restrictive as protecting the environment becomes a greater concern.
www.acr-news.com
November 2018 47
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64
