Hot-Water Supply System Pump Control for Heating Capacity Limit
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Solution Overview
Problem
Existing hot-water supply systems fail to ensure sufficient heat supply to the secondary circulation circuit when the heating capacity of the primary circuit reaches its limit, leading to insufficient temperature in the secondary circuit.
Innovation Solution
A hot-water supply and heating system that includes a heat source unit, a heat-medium heat exchanger, a primary circuit with a first pump and temperature sensor, a secondary circuit with a second pump, and controllers to manage the heating capacity and pump operation, allowing the system to adjust the secondary circuit flow rate when the primary circuit reaches its limit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the heating capacity of the heat source unit is increased to raise the primary fluid temperature, then the temperature of the first heat medium can reach the target temperature, but the system cannot effectively raise the temperature in the secondary circuit when the heating capacity reaches its upper limit
Solution Approach 1:
The system dynamically adjusts the operation frequency of the second pump based on the heating capacity status. When the heating capacity reaches the upper limit, the controller reduces the pump frequency to decrease flow rate, allowing the secondary circuit fluid to be heated to the target temperature despite the heating capacity constraint.
Solution Approach 2:
The system changes the flow rate parameter of the secondary circuit by adjusting pump frequency. By reducing the flow rate when heating capacity is limited, the system ensures sufficient heat transfer time and raises the fluid temperature to the target level without requiring increased heating capacity.
2Productivity
If the flow rate of the second heat medium in the secondary circuit is increased to improve heat distribution, then more heat can be supplied to the load, but the temperature of the fluid in the secondary circuit cannot be raised when the primary circuit heating capacity is maxed out
Solution Approach 1:
The system dynamically adjusts the operation frequency of the second pump based on real-time temperature and heating capacity conditions. When the primary circuit heating capacity reaches the upper limit, the controller automatically reduces the pump frequency to optimize the balance between heat supply amount and fluid temperature in the secondary circuit.
Solution Approach 2:
The controller continuously monitors the temperature of the second heat medium and the heating capacity status, using this feedback to adjust the pump frequency. This closed-loop control ensures that the system maintains optimal temperature and flow rate balance, raising the fluid temperature to the target level while adapting to heating capacity constraints.
3Loss of energy
If the system maintains equal flow amounts in both primary and secondary circuits to preserve heat source efficiency, then the coefficient of performance is maintained, but sufficient heat cannot be supplied to the secondary circuit when the heating capacity reaches its upper limit
Solution Approach 1:
The system transitions from a static equal-flow control strategy to a dynamic control strategy. The second pump's operation frequency is adjusted based on whether the heating capacity has reached the upper limit and whether the secondary circuit fluid temperature has reached the target temperature, allowing the system to optimize both energy efficiency and heat supply sufficiency under different operating conditions.
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 system effectively raises the temperature in the secondary circuit to the target temperature by reducing the flow rate in the secondary circuit when the primary circuit's heating capacity is maxed out, without noticeable changes to the user.
Implementation Method 1
a heat-medium heat exchanger through which the heat is supplied from the heat source unit to a load-side device; a primary circuit in which a first heat medium circulates between the heat source unit and the heat-medium heat exchanger; a secondary circuit in which a second heat medium flows between the load-side device and the heat-medium heat exchanger
Data Source
AI summary
A hot-water supply and heating system includes: a first pump that circulates a first heat medium between a heat source unit and a heat-medium heat exchanger; a second pump that causes a second heat medium to flow between a load-side device and the heat-medium heat exchanger; a first temperature sensor that detects a primary fluid temperature that is a temperature of the first heat medium that flows out of the heat source unit; a heat-source-unit controller; and a pump controller. The heat-source-unit controller transmits information indicating the heating capacity of the heat source unit reaches an upper limit value to the pump controller, when it is determined that the primary fluid temperature is lower than a target temperature and the heating capability of the heat source unit is equal to the upper limit value. The pump controller reduces an operation frequency of the second pump when receiving the above information.