NH3 Heat Pump Compressor Control for Stable Hot Water
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Heat pump units using NH3 refrigerant face challenges in maintaining stable high-temperature water supply and preventing refrigerant liquefaction, which can damage equipment due to fluctuations in load and ambient temperature, leading to increased equipment costs and potential compressor damage.
Innovation Solution
A method and unit for controlling the operation of a heat pump unit with NH3 refrigerant, involving temperature detection at the condenser or evaporator, capacity control of the reciprocating compressor through revolution-speed and cylinder-number control, and a heating mechanism to maintain the refrigerant above saturation temperature, preventing liquefaction and ensuring lubrication, while maintaining high COP.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the pressure of NH3 refrigerant is increased to produce high-temperature water, then the heating performance is improved, but the refrigerant may liquefy in the inlet pipe causing equipment damage
Solution Approach 1:
The heating mechanism heats the NH3 refrigerant in the inlet pipe before it enters the compressor, preventing liquefaction in advance. This preliminary heating action ensures the refrigerant remains in gas phase even at high pressures required for high-temperature water production, thereby preventing equipment damage.
Solution Approach 2:
The heating mechanism applies counter-heating to the refrigerant inlet pipe to offset the cooling effect that would cause liquefaction. By applying heat before the refrigerant can liquefy, the system prevents the harmful effect of liquid refrigerant entering the compressor.
2Loss of energy
If the capacity of the heat pump is varied to match load changes, then energy efficiency is improved, but the temperature control becomes complex
Solution Approach 1:
The system uses temperature detection at the condenser or evaporator outlet combined with feedback control to adjust compressor capacity. The controller continuously monitors the actual temperature and adjusts the compressor capacity accordingly, maintaining desired temperature while optimizing energy efficiency through variable capacity operation.
Solution Approach 2:
The system dynamically adjusts the compressor capacity based on real-time temperature feedback and load conditions. By making the compressor capacity variable rather than fixed, the system can optimize energy efficiency across different operating conditions while maintaining temperature control through continuous adjustment.
3Object-affected harmful factors
If CO2 refrigerant is used for high-temperature hot water supply, then environmental performance is improved, but equipment cost increases due to high pressure requirements
Solution Approach 1:
The system changes the refrigerant parameter from CO2 to NH3, which has different pressure-temperature characteristics. NH3 operates at lower pressures for the same temperature range, eliminating the need for expensive high-pressure equipment while maintaining high-temperature hot water supply capability and environmental benefits.
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
Enables stable supply of high-temperature water at desired temperatures (50-90°C) without degrading COP, preventing refrigerant liquefaction and equipment damage, and optimizing energy efficiency by maintaining the refrigerant above saturation temperature.
Implementation Method 1
a heating mechanism to maintain the refrigerant above saturation temperature, preventing liquefaction
Implementation Method 2
a condenser, an expansion valve, and an evaporator, and constitutes a heat pump cycle
Implementation Method 3
the NH3 refrigerant gas to liquefy the NH3 refrigerant gas
Implementation Method 4
having high latent heat of evaporation
Data Source
Figure 1
Figure 2~3B
Figure 3C~4B
AI summary
The temperature of high-temperature water h at the exit of a condenser 18 is maintained to be within a setting range by control of, under an operation with all cylinders, capacity of a reciprocating compressor 16 in the period between a maximum allowable load and a minimum load for lubrication, at which the flow of a lubrication oil pump 28 is capable of being ensured, based on the revolution-speed control of a drive motor 24 that drives the reciprocating compressor 16 and by control of the capacity of the reciprocating compressor 16 at the minimum load for lubrication or less based on the combination of the control of decreasing the number of operation cylinders and the revolution-speed control of the drive motor 24. In addition, a heating mechanism 70A is provided on an inlet path 14a of the reciprocating compressor 16 to prevent the liquefied refrigeration flow of a refrigerant liquid to the reciprocating compressor 16 during the operation or at the start.