Heat Pump Coil Flow Control for Uneven Airflow
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Solution Overview
Problem
Air-water heat pumps with multiple expansion valves are costly and complex to install and calibrate, and uneven air flow through finned coils can lead to inefficient heat exchange due to differences in heat exchange performance among coils, resulting in suboptimal refrigerant fluid phase and reduced system efficiency.
Innovation Solution
An air-water heat pump design utilizing a single expansion valve and electronic control unit with temperature sensors to regulate the mass flow of refrigerant fluid through each finned coil, ensuring all coils operate with refrigerant in the superheated steam phase by adjusting the flow rate based on temperature differences, thereby compensating for reduced heat exchange in any coil.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple expansion valves are used to ensure equal refrigerant flow to each finned coil, then the heat exchange efficiency is improved, but the device complexity and installation cost increase
Solution Approach 1:
The patent merges multiple expansion valve functions into a single expansion valve that serves all finned coils. The refrigerant distribution system is designed so that one expansion valve can evenly distribute refrigerant to multiple coils through proper piping configuration, eliminating the need for multiple separate valves while maintaining equal flow distribution.
Solution Approach 2:
The single expansion valve is designed to perform the function of multiple valves by being positioned and configured to distribute refrigerant to all finned coils universally. The valve serves as a common distribution point for the entire evaporator assembly, replacing the need for coil-specific valves.
2Ease of manufacture
If a single expansion valve is used to reduce complexity and cost, then the installation and manufacturing are simplified, but the refrigerant flow distribution to finned coils becomes uneven
Solution Approach 1:
The patent applies local quality by positioning the single expansion valve and its associated piping to create equal flow paths to each finned coil. The refrigerant distribution manifold or piping configuration is specifically designed with equal lengths and resistance characteristics to each coil, ensuring uniform flow distribution despite using a single valve.
3Volume of moving object
If finned coils are arranged in adjacent pairs to save space, then the compactness is improved, but the ventilation channel between internal coils reduces heat exchange performance
Solution Approach 1:
The patent introduces a controllable flow resistance element (such as an adjustable valve or variable restriction) in the refrigerant line serving the internal finned coils. This dynamic element allows the system to compensate for the reduced heat exchange performance by adjusting refrigerant flow distribution in real-time, maintaining optimal operation despite the compact arrangement.
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 design simplifies installation, reduces costs, and maintains high efficiency by ensuring uniform refrigerant flow and phase across all coils, preventing overheating and maintaining optimal operation despite variations in air flow and heat exchange performance.
Implementation Method 1
an evaporator assembly, which is designed to absorb heat from the air by evaporation of the refrigerant fluid
Implementation Method 2
a compressor for compressing the refrigerant fluid
Implementation Method 3
a condenser assembly, which comprises at least one heat exchanger for transferring heat from the refrigerant fluid to a second fluid, in this case water
Implementation Method 4
it is in the superheated steam phase at the outlet of the evaporator assembly, in the liquid phase at the inlet of the expansion valve
Implementation Method 5
at least one expansion or throttling valve, which is connected to the inlet of the evaporator assembly to reduce the pressure of the refrigerant fluid before it enters the finned coils
Data Source
Figure 1
AI summary
A heat pump comprising a condenser assembly (7), a single expansion valve (9) connected to the outlet of the condenser assembly (7), and an evaporator assembly (4) having finned coils (5a-5d) connected in parallel to the outlet (9a) of the expansion valve (9) through respective ducts (17a-17d), and ventilation means (10) for forced ventilation of the finned coils (5a-5d). At least a first finned coil (5a) is arranged so as to receive a reference air flow rate, and at least a second finned coil (5c) is arranged so as to receive an air flow rate lower than the reference air flow rate. The heat pump (1) has at least two sensors (14, 15) for measuring two respective temperatures (Ta, Tc) of the refrigerant fluid at the outlet of the first finned coil (5a) and at the outlet of the second finned coil (5c), respectively. Only the duct (17c) of the second finned coil (5c) is provided with a flow control valve (16). The heat pump (1) has an electronic control unit (18) configured to control the flow control valve (16) as a function of the two temperatures (Ta, Tc).