Large heating and cooling systems are oversized because the system and its components are based on delivering full load in the most extreme weather conditions. Designing a system for full load, however, does not mean that its performance will be optimal for the 310 days of a year that it will be running on partial load. A less than optimal performance is often at the expense of user comfort, because under partial load the system is likely to be out of balance hydraulically.
Hyspot’s hydraulic design and simulation software is claimed to optimise the performance of a system to unlock yearly project and energy savings of up to 40%, with an investment payback typically between one and five years. What’s more, it is claimed that savings of up to 20% can be obtained through minor hydraulic adjustments and tweaks to the control strategy, often without any capital expenditure.
The software was developed because a large heating or cooling installation can have hundreds or even thousands of valves and if you change the resistance of one valve, flow rates throughout the whole circuit might, potentially, be affected. And changing the flow rate can alter the quantity of heat or cooling delivered to a particular space because water in the system will flow along the path of least resistance
The problem is best explained using the example of a radiator system. If there were no valves on the system then the path of least resistance for the heat transfer fluid will be through radiators nearest the pump, which will then give off the most heat. The radiators further from the pump may have insufficient heat, which could result in one room being too hot while another is too cold. To balance the system resistance is artificially increased on circuits nearest the pump and decreased on circuits further away from the pump using valves until the system is balanced with the correct flow rate throughout the entire circuit. Simple.
However, if a valve is adjusted or the temperature in the circuit or a room changes, then the system will cease to be in balance. To optimise the flows throughout a system, designers need to take all possible variable conditions into account, such as component properties, pressure, temperature and valve positions because the installation will behave differently under different degrees of partial loading. In addition, individual users might want to adjust flow rates so that their space is slightly warmer or cooler than others.
The only way to ensure optimum system flows is to calculate the behaviour of each component in an installation under all possible conditions - no small feat when you consider that some 50 million calculations are necessary even for a small installation rising to over a billion for a large campus, hospital or district heating network.
Hysopt’s software has been developed specifically to simulate and calculate precisely how each component will behave in all possible conditions and the impact of each component on the entire system. Only by placing the entire HVAC installation in a digital model and calculating permutations mathematically is it possible to obtain the optimal plan for an efficient installation capable of delivering comfort conditions.
How does the software work?
• The first step is to build a digital model of an installation using a models library and pre-programmed hydraulic circuits to create a visual representation of a system. During this step the software will automatically warn of faults in the design - forgotten control valve, pump too small, incorrect flow rate - so that the model is correct from the outset.
• With the model complete, the software can now start the simulation. Initially, it finds the best general concept. Algorithms then optimise component selection
• The software then has the facility to simulate how the installation will behave with integrated renewable energy, for example by subjecting it to variable weather conditions or with the addition of a CHP system to evaluate energy consumption, thermal behaviour and control.
• When all the calculations have been made, users are able to compare different designs to see which delivers the biggest energy savings and lowest carbon emissions and which solution requires the largest capital investment, for example.
• The selected design is then optimised using the software to calculate which equipment and dimensions are most suitable for that particular installation. The software provides information about each component’s adjustment – in effect providing detailed operating instructions for the installation and regulation of all components
• By linking the model to a dynamic building model (exposed to weather data and room set point profiles) the system’s simulation capability can predict system performance and heating or cooling energy consumption during the design phase in addition to quantifying auxiliary energy used by pumps and fans.
By placing the entire HVAC installation in a digital model and fully calculating everything mathematically correctly, an optimal plan for an efficient, comfortable installation can be established.