Heat Exchanger Valve Control for Stable Hot Water Temperature
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Solution Overview
Problem
Existing heat extraction devices from district heating systems face challenges in maintaining a constant fluid outlet temperature, experiencing temperature fluctuations, and high operational losses due to varying pressures and temperatures, leading to inefficiencies and maintenance issues.
Innovation Solution
The implementation of temperature sensor-controlled valves at both the heat transfer medium inlet and outlet of the heat exchanger, allowing for precise control of heat transfer medium flow and return temperature, utilizing straight-way or three-way mixing valves to ensure consistent fluid outlet temperature and minimize losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a proportional control valve is used to regulate heat transfer medium flow, then the fluid outlet temperature can be controlled, but temperature fluctuations occur and the system requires high cold water pressure (2-2.5 bar minimum)
Solution Approach 1:
A temperature sensor is introduced as an intermediary between the proportional control valve and the fluid outlet temperature. The sensor continuously monitors the outlet temperature and provides feedback to the control unit, which then adjusts the valve position accordingly. This closed-loop control mechanism eliminates temperature fluctuations without requiring high cold water pressure, as the system adapts to varying pressure conditions through active feedback control.
2Quantity of substance
If a mixing valve is used in the heat carrier flow to short-circuit part of the heat exchanger, then smaller amounts of hot water can be taken, but larger amounts of heat are only available after a certain lead time
Solution Approach 1:
The system dynamically adjusts the mixing valve position based on real-time hot water demand and heat carrier temperature conditions. Rather than a fixed short-circuit arrangement, the valve continuously modulates to optimize the balance between immediate hot water availability and heat extraction efficiency. This dynamic control allows the system to respond instantly to demand changes while maximizing heat recovery from the heat carrier.
3Ease of operation
If proportional controllers are used for heat extraction, then pressure and temperature control is achieved, but the controllers are very expensive to construct and can only be used up to a certain flow rate
Solution Approach 1:
The complex mechanical proportional controller is replaced with a simpler electronic control system consisting of a temperature sensor, control unit, and electronically actuated valve. The electronic system provides equivalent or superior pressure and temperature control capabilities while being less expensive and capable of handling higher flow rates. The control unit processes sensor signals and drives the valve using electronic actuators, eliminating the need for complex mechanical linkage and spring mechanisms.
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
This solution enables rapid response to heat demand, maintains fluid outlet temperature fluctuations below 0.5°C, reduces operational losses, and ensures immediate availability of hot water without requiring separate bypasses or increased cold water pressure, thereby minimizing maintenance and energy wastage.
Implementation Method 1
a heat exchanger (2) through which heat transfer medium flows on the one hand and a fluid to be heated (WW), in particular drinking water, on the other hand
Implementation Method 2
releasing heat and the heat transfer medium is then returned
Implementation Method 3
The fluid to be heated, in particular drinking water, flows through the heat exchanger unit in such a way that it is brought to a desired, presettable temperature in countercurrent to the heat exchanger
Implementation Method 4
a first temperature sensor (4)-controlled valve (3) being arranged in the heat transfer medium inlet to the heat exchanger (2)
Implementation Method 5
a valve for controlling the amount of heat transfer medium conducted through the heat exchanger (2)
Data Source
Figure 1
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AI summary
A device is proposed for extracting heat from a heat transfer medium with a heat exchanger through which the heat transfer medium flows on the one hand and a fluid to be heated on the other hand and with a valve for regulating the amount of heat transfer medium conducted through the heat exchanger. For the advantageous removal of heat, a temperature sensor-controlled valve is arranged in the heat carrier inlet to the heat exchanger, the associated temperature sensor of which is arranged in the fluid outlet of the heat exchanger in order to achieve an at least approximately constant fluid outlet temperature, and that in the heat carrier outlet (RL) of the heat exchanger (2) there is a temperature sensor-controlled valve (5 ) is arranged, the associated temperature sensor (6), to limit a desired heat carrier return temperature, in the fluid inlet (KW) of the heat exchanger (2) is arranged.