Optimising the Number of Pumps and Balancing Valves in Chilled Water Distribution Systems

Adrian Retezan,Szilveszter Geyer Ehrenberg,S.I Tanabe,J Kurnitski,H Zhang,P Wargocki,G Cao,L Mazzarela,M.C Gameiro Da Silva,I Nastase,C Inard

doi:10.1051/e3sconf/201911101071

Abstract

Everyday life does involve use of cooling systems for different areas and scenarios. We use them to keep our thermal comfort level at optimum, either to get rid of some extra heat from technological systems. From various cooling solutions, one and very common system is the chilled water system, where centralised chiller plants produce the cooling energy and all terminal units do receive cooling energy using a distribution loop. According to statistical data, electrical energy consumption of pumps might be up to 17% of entire electrical use of the cooling plant. When designing our cooling system loads during operation will not be same all the time. Variation must be treated accordingly, therefore to get best efficiency of the system, we must get a good control. Beside shut-off motorised valves our balancing must be considered in different scenarios. The paper looks to summarize the challenges in getting a good balancing and energy efficiency in chilled water distribution system.

Highlights

Everyday life does involve use of cooling systems for different areas and scenarios
- Pressure losses on heat exchanger coils. Considering all these items we could see that in case of pressure losses, pipe lengths will be defined by the optimum piping route, with corresponding section
When we put valves to control a constant pressure loss, or to balance the system we lose some energy, which we introduced at the source

Summary

General Challenges of Distribution Loop

Everyday life does involve use of cooling systems for different areas and scenarios. We use them to keep our thermal comfort level at optimum, either to get rid of some extra heat from technological systems. As flow is given in HVAC systems by relation of thermal energy and temperature difference, pressure losses are defined by sum of local pressure losses across pipes, heat exchangers and all sort of control and balancing valves. Considering scenario a), it means that we will install several pumps in parallel, so it will work in low conditions possible with higher or at least similar efficiency In this case we still have to deal with the fact, that large distribution loops considered as one main loop will have installed several balancing valves in series, so total pressure drop summarised across balancing valves will be significant. Scenario b.), will make a split of the system, so we will deal with smaller loops, which will reduce the stress on the valves, we could use smaller pumps and reliability will be much higher

ON-OFF control valves

H Average

Findings

Conclusions