The Thermo-Differential Stratification Valve is a unique self-actuating 3-way switching valve for enhancing the stratification in thermal storage tanks, which have inlet flows with variable inlet temperatures, such as the inlet flow from a solar thermal heat source, the return flow from a domestic hot water (DHW) station with circulation, or the return flow from space heating (using radiators). The valve enhances the stratification by directing the inlet flow into the upper region of the tank when it is sufficiently hot (at least as hot as the upper region of the tank), and directing it to the lower region of the tank when it is not, thereby boosting the storage tank’s performance and thermal efficiency.
The Thermo-Differential Stratification Valve is installed directly on the storage tank inlet and uses an extremely reliable switching mechanism to direct the flow to different levels in a storage tank, based on the temperature difference between the water flow through the valve and the water inside the storage tank, as illustrated by the animation below.
Besides directing the flow to different levels in a single storage tank, the Thermo-Differential Valve can also bypass a storage tank and direct the flow to a second storage tank, creating a stratified cascade arrangement of multiple storage tanks.
The self-actuating technology (patent pending) of the actuator is based on mass-transfer inside the actuator, which consists of a float sticking into the tank and a small container inside the valve, connected by a rigid, thin tube. The mass transfer inside the actuator is driven by vapor pressure differences; the higher vapour pressure in the warmer part of the actuator pushes all the liquid towards the cooler part of the actuator, regardless of what the temperature levels are; it responds purely to temperature difference. As the liquid inside the actuator flows from the warmer section to the cooler section, there is a change in the buoyancy of the float, which sinks when it is filled with liquid (i.e. when the temperature in the tank is lower than inside the valve), but floats when it is filled with vapour. This change in buoyancy of the float is what actuates the valve (with the buoyancy force amplified many times through leverage in the pivoting mechanism), the actuation/switching is illustrated by the animation below.
Click on the valve to see how it changes position in response to a change in temperature difference between process flow and storage tank
This novel and patented actuation principle only requires a very small temperature difference (< 0.5 K) for the actuator to exert its full switching force, and the reaction/switching time of the actuator decreases with increasing temperature difference, allowing the valve to respond in less than 10 seconds to large changes in temperature difference. The actuator has a very straightforward working principle, which does not use any springs or membranes (actuator completely made of stainless steel), and the actuator is completely integrated into the valve, so there is no risk of the valve leaking through dynamic seals, which makes the Thermo-Differential Stratification Valve extremely reliable and durable. While there is no electrical actuator, the Thermo-Differential Stratification Valve can be completely insulated using its EPP insulation shell, reducing heat losses, and it has a flow diverter disc fitted to the actuator as standard, which minimizes the inflow disturbance in the tank, ensuring a slow, gentle flow into the tank.
The Thermo-Differential Valve enhances the performance and efficiency of thermal storage systems by directing the water flow to the most appropriate level of the storage tank, thereby creating and maintaining a high degree of thermal layering (stratification) in the storage tank of storage systems, where one (or more) of the flows into the tank is variable in temperature Thermal storage systems benefit from a high degree of thermal layering in the storage tank, because this prevents the heated water in the top of the tank from mixing with colder water below, which increases the output performance of the storage system, and it also prevents the cold water in the bottom from mixing with warmer water above, which increases the efficiency of heat sources such as solar, heat pumps, and also of condensing boilers.