Water systems
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Solution Overview
Problem
Large hot water systems in commercial settings face challenges in maintaining sanitary conditions due to bacterial growth, particularly Legionella bacteria, as existing systems struggle to prevent the formation of bacterial colonies in pipes during periods of non-use, leading to potential health risks.
Innovation Solution
A circulating hot water system with concentric outflow and return conduits that eliminate dead legs, combined with a control system and novel valve design, ensures continuous circulation and heating, preventing bacterial growth by maintaining water at adequate temperatures and using a pressurized external supply to compensate for water taken at outlets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If water is circulated continuously through the system to maintain hot water availability at outlets, then hot water supply reliability is improved, but bacterial growth is promoted during periods of non-use when water cools in pipes
Solution Approach 1:
The system segments the water circulation by introducing separate circulation pumps for different zones or circuits, allowing selective circulation in active areas while maintaining stagnation in inactive areas, thus preventing bacterial growth where water is not needed while ensuring hot water availability where it is required
Solution Approach 2:
The system implements periodic circulation cycles where water is circulated during periods of use and allowed to stagnate or be heated to bactericidal temperatures during periods of non-use, rather than maintaining continuous circulation throughout the entire system
2Reliability
If large volumes of water are stored in the system to ensure adequate hot water supply, then hot water availability is improved, but energy consumption increases due to continuous heating requirements
Solution Approach 1:
The system dynamically adjusts circulation flow rates and heating power based on detected water demand signals from outlets, reducing or stopping circulation and heating in areas with no current or anticipated demand, thereby maintaining hot water availability where needed while minimizing energy consumption in inactive areas
3Speed
If circulation flow rate is increased to reduce water cooling in pipes, then hot water delivery speed is improved, but energy loss from heat dissipation increases
Solution Approach 1:
The system applies different circulation flow rates to different parts of the system based on local demand characteristics, maintaining higher flow rates in zones with frequent or immediate water usage while using lower or zero flow rates in zones with infrequent or delayed usage, thus optimizing both delivery speed and energy efficiency locally
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively inhibits bacterial colony formation, ensures a reliable hot water supply, reduces energy consumption, and maintains safety by preventing scalding, while allowing for pasteurization modes to ensure decontamination.
Implementation Method 1
a heater 102... Heating in the heater 102 is usually by a closed-circuit heat-exchange element heated by fluid circulating via an electrically- or gas-heated boiler
Implementation Method 2
Heating in the heater 102 is usually by a closed-circuit heat-exchange element heated by fluid circulating via an electrically- or gas-heated boiler
Implementation Method 3
A pump 103 circulates hot water continuously around the circuit 101
Implementation Method 4
a temperature sensor 105 is provided on the return pipe and connected (e.g. via a transducer or temperature control device 106) to a hot water control system 107
Data Source
AI summary
A circulating hot water system has a hot water flow circuit defined by pipework leading out from and back to an in-line heater, and including a pump to drive circulation of the hot water. Each of multiple user points has an outflow branch conduit and a return flow branch conduit with a common wall for heat exchange, as does the main flow circuit: the outflow conduit surrounds the return conduit. Water is fed into the system from a pressurized cold water supply main through a check valve. Sensors are used to monitor water temperatures and flow conditions around the system. A programmed control processor can control heating and pumping rates in various regimes, e.g. to maintain system temperature above a predetermined threshold. An isolation valve adapted for concentric double pipes is also described.