Chilled Water Buffer Vessels / Tanks for Efficient Chilled Water HVAC Systems

 

Chilled water buffer vessels or a chilled water buffer tank help air conditioning systems’ chillers avoid excessive cycling and temperature control issues; as a solution, low water volume systems may require the installation of additional buffer capacity to prevent rapid cycling of the chiller and operate efficiently.

The distribution system and the chillers are separated by these chilled water buffer tanks or buffer vessels.

In essence buffer tanks or vessels for chilled water are used to provide additional storage capacity for the chilled water system to cover high system demands and to prevent rapid cycling of the chiller units.

All our buffer tanks for a chilled water system are in full compliance with the European PED regulations and are only to be used on a sealed system i.e. an unvented chilled water system.

Chilled water thermal storage tank fundamentals

Opposite to a heating system buffer vessels which are used to collect heat in the form of hot water from biomass boilers, a heat pump heat source or other renewable energy systems such as solar, a chilled water buffer tank or buffer vessel may also be used to balance the loads and demands of commercial operations throughout the day by adding additional volume to the chilled water system. This increases the cooling system’s durability and dependability while lowering maintenance needs.

A heat pump can be a reversible type, so it can produce heat energy via hot water for the heating system and then chilled water for cooling purposes.

How do you size a chilled water buffer vessel?

• The size of a chilled water buffer vessel depends on the chilled water system’s application, output, and additional volume demand.
• The size of the buffer tanks should be based on operation needs, installation, and maintenance requirements.

Chillers should not start more than six times per hour; some manufacturers recommend three. As a result, capacity is required to ensure that the distribution volume is large enough to handle the chiller’s thermal input. Allow 10 or even 20 minutes of minimum operating time as a rule of thumb to prevent prevent rapid cycling of the chillers.

For most cooling or chiller applications

The system use method requires a minimum of 4 litres per kW for air conditioning and a minimum of 7 litres/kW for process cooling buffer tanks.

A rule of thumb for sizing is to allow 2.5 to 8 litres per kW for the majority of applications and up to 14 litres per kW for the chilled water thermal storage tank when temperature accuracy is critical.

We go into full detail on buffer tank sizing for chilled water systems on this dedicated webpage – chilled water buffer tank sizing

Always take the chiller manufacturer’s recommendations or requirements as precedence, as various control systems and differences in turn-down ratios between manufactured units will mean that the thermal storage tank for chilled water system size can vary dramatically between manufacturers.

Chilled water thermal storage tank product range

We have a few options for chilled water buffer tanks, these are separated by tapping port sizes and/or the number of connecting tappings, so we can supply the ideal solution for your system requirements for additional volume.

Option 1: Our “PSS” range of buffer vessels

 

• 6 bar working pressure rated chilled water storage tank range.
• Mild / Carbon steel construction.
• 25 litre to 2,000 litre chiller buffer tank storage capacities.

 

Then our 500 litre to 2,000 Litre “PSS” Buffer vessels / buffer tank for chilled water units.

• Chilled water buffer vessels with either a four connecting tappings range or a six connecting tappings range

• Buffer tank for chilled water range with mild steel construction with the inside untreated and the outside coated.
• This buffer vessel for chilled water range conform to all parts of the European PED directive.
• ErP “C” or above insulation ratings, where relevant.
• Our buffer vessels feature three instrument pockets for temperature sensors or gauges, unlike our competitors’ standard two instrument pockets.
• Our chilled water buffer tank range come with insulation jackets for internal plant room use, optional ultra-volilet-resistant jackets for external mounting, or aluminium insulation shells (normally for external mounting in coastal areas) for external mounting, depending on your site requirements.

Full details on this “PSS” range of chilled water buffer vessels are here:

Download the PPS Buffer tanks for chilled water – 25 litres to 2,000 litres capacity brochure from Flexiheat UK

Option 2: Our range of ACF chilled water storage tanks –

• 10 Bar working pressure rated from 25 to 1,000 Litres.
• 6 Bar rated from 1,500 to 5,000 Litres chilled water storage tank models.
• Mild steel or carbon steel construction.
• Four connecting tappings – marked the “DN1’s “on the following diagram.

• Removable insulation panels are on our 800 and 1000 Litre units that allow the buffer vessels to pass through a standard 800mm wide doorway.
• Three temperature sensor or gauge tapping’s (instrument pockets) on this chilled water buffer tank range
• Option of an embossed aluminium covering for external mounting of these chilled water buffer tanks

Full detail on this range of chilled water buffer tanks is here:

Download the ACF Buffer vessels for chilled water or heating water HVAC systems brochure – Flexiheat UK

Construction of the Vessels

Material Selection: Mild Steel or Stainless Steel

• Chilled water buffer tanks or vessels can be manufactured in various materials, including mild steel, carbon steel, or stainless steel. A buffer vessel for chilled water typically uses mild steel as its standard material.
• Stainless steel buffer vessels for chilled water systems benefit from increased durability when compared to mild steel buffer tanks.

The benefits of HVAC system efficiency and energy savings are significant

• Buffer vessels enhance system efficiency by reducing pump cycling and minimising energy consumption of the chiller.
• In chilled water applications, chilled water buffer tanks stop the chillers from cycling quickly and helps maintain efficiency.
• They prevent pressure surges and the water hammer effect, extending the lifespan of pumps and valves.

Common applications for chilled water systems

Commercial applications like large data centres and server rooms are increasingly using chilled water (CHW) systems via water cooling fan coil units,chilled beams or air handling units to cool their indoor air and equipment.

• Buffer vessels are used in HVAC systems to avoid the rapid cycling of chillers in low water volume systems.
• A chilled water storage tank are commonly used in commercial and industrial buildings, data centres, and telecommunication facilities for climate-controlled environments.

Contact Us

Our expert team at Flexiheat UK is on hand for technical support and to talk you through our full range of chilled water buffer tanks or chilled water buffer vessels that we can supply. If you require any further assistance, please click here to contact us via email or call us directly at 01202 822221.