Thermal Energy Recovery Evaporator Startup Control
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Solution Overview
Problem
Conventional thermal energy recovery devices experience rapid temperature increases and thermal stress in the evaporator during startup when using steam as a heating medium, leading to potential damage and inefficiencies.
Innovation Solution
A thermal energy recovery device with a controlled heating medium flow adjustment system that gradually increases the inflow of steam to the evaporator, stopping the pump until the evaporator reaches a specified temperature to prevent sudden temperature rises and incorporating a steam trap and pressure management to prevent water hammer phenomena.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the pump is driven before the evaporator reaches specified temperature, then the working medium circulates and heats up faster, but the heating medium condenses rapidly causing sudden temperature rise and thermal stress
Solution Approach 1:
The pump is stopped during the initial heating phase until the evaporator reaches a specified temperature. This preliminary action prevents the working medium from circulating too early, thereby avoiding rapid condensation of the heating medium and the resulting sudden temperature rise and thermal stress in the evaporator.
Solution Approach 2:
The control unit monitors the evaporator temperature and uses this feedback to control the pump operation. When the temperature reaches the specified value, the control unit activates the pump; otherwise, it remains stopped. This feedback mechanism ensures the pump operates only when appropriate, preventing thermal stress while maintaining heating efficiency.
2Temperature
If the heating medium flow is increased rapidly, then the evaporator heats up faster, but thermal stress increases rapidly causing potential damage
Solution Approach 1:
The system dynamically adjusts the heating medium flow rate based on the evaporator's temperature conditions. During startup, the flow rate is controlled to increase gradually rather than abruptly. The control unit regulates the flow adjustment unit to match the heating medium supply rate with the evaporator's thermal capacity, preventing excessive thermal stress while maintaining efficient heating.
Solution Approach 2:
The flow rate of the heating medium is changed as a variable parameter based on evaporator temperature. The control unit adjusts the flow rate from a lower initial value to a higher value as the evaporator temperature increases, ensuring the heating process matches the structural承受能力 of the evaporator and avoiding rapid thermal stress.
3Productivity
If the pump operates at high speed, then the working medium circulates faster improving efficiency, but water hammer phenomena occur due to pressure imbalances
Solution Approach 1:
The pump is started at a low speed initially to establish proper pressure conditions in the system before increasing to high speed. This preliminary low-speed operation allows the pressure distribution to stabilize, preventing water hammer phenomena when the pump subsequently operates at high speed for improved efficiency.
Solution Approach 2:
The pump operates in a staged manner with periodic speed adjustments. It starts at low speed, maintains operation until temperature conditions are met, then transitions to high speed. This periodic speed adjustment pattern prevents sudden pressure changes that cause water hammer while maintaining overall system productivity.
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 suppresses rapid temperature increases and thermal stress in the evaporator, ensuring stable operation and preventing water hammer phenomena, thereby enhancing the device's efficiency and longevity.
Implementation Method 1
an evaporator for evaporating a working medium by allowing a heating medium in a gas phase supplied from the outside and the working medium to exchange heat therebetween
Implementation Method 2
a preheater for heating the working medium by allowing the heating medium flowing out of the evaporator and the working medium before flowing into the evaporator to exchange heat therebetween
Implementation Method 3
a condenser for condensing the working medium flowing out of the expander
Data Source
AI summary
A thermal energy recovery device capable of suppressing a rapid increase of thermal stress generated in an evaporator when the operation is started and a start-up method thereof are provided. The thermal energy recovery device includes an evaporator, a preheater, an energy recovery unit, a circulating flow path, a pump, a heating medium flow path for supplying a heating medium to the evaporator and the preheater, a flow adjustment unit provided in a portion on the upstream side than the evaporator within the heating medium flow path, and a control unit. The control unit controls the flow adjustment unit so that the inflow amount of the heating medium in a gas-phase to the evaporator gradually increases, in a state that the pump is stopped, until the temperature of the evaporator becomes a specified value.