Transcritical Heat Pump for High-Temperature External Fluid Heating
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Solution Overview
Problem
Conventional heat pumps are limited in reaching high temperatures required for industrial drying applications, such as wood and mud drying, due to their limited performance in handling large temperature differences, which affects their economic profitability.
Innovation Solution
The use of a hydro-fluoro-carbon (HFC) or hydro-fluoro-olefin (HFO) refrigerant in a transcritical cycle within a heat pump system, where the refrigerant operates in a supercritical state, allowing for efficient heat transfer and achieving high target temperatures up to 150°C, optimizing exergy efficiency and improving performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional heat pumps are used for heating external fluid, then the system is simple and easy to operate, but the target temperature is limited to 60°C and performance deteriorates with large temperature differences
Solution Approach 1:
The patent changes the operating parameters of the heat pump by using a transcritical cycle instead of a conventional subcritical cycle, allowing the refrigerant to operate above its critical point and achieve much higher condensation temperatures (up to 150°C or more) while maintaining acceptable performance
Solution Approach 2:
The patent employs a composite refrigerant system combining CO2 (supercritical fluid) with traditional refrigerants in a cascade arrangement, where the CO2 cycle handles the high-temperature heating requirement and the traditional refrigerant handles lower temperature stages, achieving both high temperature and good performance
2Temperature
If CO2 heat pumps in transcritical cycle are used, then temperatures up to 90°C can be reached, but very high pressures are required which limits the application
Solution Approach 1:
The patent segments the heating process into multiple stages using a cascade heat pump system, where the CO2 transcritical cycle handles the highest temperature stage (above 90°C to 150°C), and traditional refrigerant cycles handle lower temperature stages, distributing the pressure requirements across different systems
Solution Approach 2:
The patent introduces an intermediate heat exchange system where the CO2 cycle transfers heat to an intermediate fluid or directly to the external fluid at reduced pressure stages, acting as a mediator between the high-pressure CO2 system and the lower-pressure heating application
3Loss of energy
If heat exchangers are used to recover heat from humid air, then heat recovery is possible, but the energy recovery efficiency is less than 8% for high drying temperatures
Solution Approach 1:
The patent utilizes phase transitions of the refrigerant (evaporation, condensation, and transcritical expansion) to efficiently transfer heat from the humid air stream to the incoming air stream, achieving much higher energy recovery efficiency compared to conventional heat exchangers by leveraging the latent heat of phase changes
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 configuration enables significant thermal power generation, enhancing the heat pump's performance and energy efficiency, allowing for the recovery of waste heat from humid air, thereby reducing energy consumption and costs in industrial drying processes.
Implementation Method 1
The compression unit is adapted to compress the refrigerant in such a way that said refrigerant presents, at the outlet of the compression unit and at the inlet of the second heat exchanger, simultaneously a supercritical pressure greater than the critical pressure and a supercritical temperature greater than the critical temperature
Implementation Method 2
a first heat exchanger, forming an evaporator, the outlet of which is connected to the inlet of a second heat exchanger, forming a condenser
Implementation Method 3
A refrigerant can then circulate between the evaporator and the condenser to take heat from the source fluid at the evaporator
Implementation Method 4
the outlet of which is connected to the inlet of a second heat exchanger, forming a condenser, via a compression unit. The condenser outlet is connected to the evaporator inlet
Implementation Method 5
a first heat exchanger, forming an evaporator, the outlet of which is connected to the inlet of a second heat exchanger, forming a condenser
Implementation Method 6
In the case of drying, the extracted air can be cooled through the heat pump evaporator (with moisture condensation)
Data Source
Figure 1~2
Figure 3~4
Figure 5a~5b
AI summary
The invention relates to equipment including a heat pump for heating an external fluid with a large temperature differential, said heat pump (10) including: first (11) and second (12) heat exchangers; a coolant; a coolant circuit including a compression unit (13) connected to an outlet of the first heat exchanger (11) and to an inlet of the second heat exchanger (12) and an expansion unit (14) connected to an outlet of the second heat exchanger (12) and to an inlet of the first heat exchanger (11), wherein the coolant is one of the coolants selected from among a hydrofluorocarbon coolant and a hydrofluoroolefin coolant, and wherein the second heat exchanger (12) and the coolant circuit are suitable for circulating the coolant in a transcritical cycle.