Constant Volume Variable Core Radial Diffuser (RVD)
The RICKARD Constant Volume Radial Vane Diffuser with adjustable flow (Type RVD) is primarily intended for buildings where good air mixing is required. They are ideal for installations with ceiling voids in excess of 3.8m and where improved occupant comfort is called for in both heating & cooling modes.
Due to their ability to achieve a rapidly spreading swirl throw pattern with fast velocity decay and high induction rates, these diffusers are best suited to provide high air volume flow rates without drafts at occupant levels. The flow pattern may be adjusted manually with the manual mechanism or automatically with the thermal mechanism between a conical swirl flow pattern for cooling mode to a vertical column with a secondary conical swirl flow pattern for heating mode.
The functionality and affordability of the thermal mechanism makes this option the obvious choice for heating and cooling applications.
High induction rates for large volume applications.
No regular maintenance is required.
The focus of the design was to offer high comfort levels by offering the required diffuser performance with the lowest pressure drop possible.
AESTHETICS AND CONSTRUCTION
Designed with simplicity and functionality in mind the Rickard range of RVD’s compliments most of today’s large modern spaces.
The RVD is constructed of sheet steel. Each RVD is degreased, primed and finished in our standard semi-matt white chip resistant baked epoxy powder coating. A wide range of colour requirements can be met with our epoxy coating or wet spray options.
Rickard warrants it Manual and Thermal RVD for a period of 10 years.
AREAS WITH CEILING VOID HEIGHTS GREATER THAN 3.8M
Cools the space with a conical swirl flow pattern of cold or isothermal air.
Heats the space with a vertical column with a secondary conical swirl flow pattern of air that has a temperature differential between –10k and +15k.
INTERNAL ZONES WITH A CONSTANT LOAD
THE MANUAL CHANGEOVER MECHANISM CAN BE USED FOR HEATING ONLY OR COOLING ONLY APPLICATIONS
The mechanism can be switched between modes in summer and winter if there is physical access.
THE THERMAL CHANGEOVER MECHANISM CAN BE USED FOR HEATING AND COOLING APPLICATIONS.
The mechanism will automatically switch between modes.
BUILDINGS THAT NEED EXCELLENT AIR MIXING.
WHERE HIGH AIR VOLUME FLOW RATES AND THE ABSENCE OF DRAFTS AT OCCUPANT LEVELS IS REQUIRED.
The RVD range is equipped with either a Thermal or Manual flow pattern mechanism for heating or cooling applications. The position of the perforated butterfly damper located in the core of the diffuser is varied.
The Thermal mechanism automatically switches the butterfly damper located in the core between the closed and open position. When the core is open, the RVD blows air in a vertical column with a secondary conical swirl flow pattern for heating. The supply air temperature should be greater than 31°C or 88°F for the heating mode to be fully activated. When the core is closed, the RVD blows air in a conical swirl flow pattern for cooling. The supply air temperature should be less than 24°C or 75°F for the cooling mode to be fully activated.
AUTOMATIC THERMAL CHANGE OVER MECHANISM
The Manual mechanism has a lever fitted to the side of the RVD and moves the damper so that the supply air discharge can be varied between a vertical column with a secondary conical swirl flow pattern for heating to a conical swirl flow pattern for cooling. Setting the manual damper between the full horizontal and vertical pattern creates a combination of the two patterns.
MANUAL CHANGE OVER MECHANISM
The most important practical factors to consider in internal zones are noise levels and uniform air distribution without "dumping" effects. "Dumping" is the tendency for cold, dense air to leave the diffusers as a vertical column similar to a waterfall. The effect of dumping is to overcool the person immediately below the diffuser while the person further away will not be cooled enough.
Dumping is eliminated by ensuring that the discharge air energy from the diffuser is adequate to distribute conditioned air evenly throughout the conditioned area and at the same time provide good secondary room air induction rates. Providing the total pressure in the neck of the RVD selected is not too low, dumping of conditioned cold air will not take place. The RVD is designed to avoid the tendency to dump.
A rapidly descending flow pattern similar to dumping can occur when two air streams travelling in opposite directions meet. This tendency is substantially reduced with the use of radial diffusers, but it can be avoided completely by ensuring that RVD’s are placed far enough apart to eliminate drafts in the conditioned spaces. The Rickard RVD’s flow pattern in cooling spreads outwards and downwards in a cone of air. The angle of the cone is approximately 24 degrees from the verticl. The swirl effect creates a rapid decay in velocity with high induction rates. Using this information, RVD’s should be situated in the ceiling such that two adjacent diffusers are separated by slightly less than the sum of their cone diameter at floor level. Exactly how much less depends largely on the ceiling height and the amount of air movement desired in the conditioned space.
In heating the Rickard RVD's pattern is a vertical column to get the air down and uses a secondary conical swirl flow pattern to mix and induce the air in the room.
Rickard’s range of RVD’s comes in 3 sizes, namely a 315, 400 and a 630mm diameter unit.
A thermal and manual mechanism is available for changeover between heating and cooling.
Top entry round and side entry square plenums are available as an optional extra.
Entry plenums constructed from coated or uncoated mill galvanized sheet steel are also available.