Heat ventilation and air conditioning unit
Solution Overview
Problem
Existing air conditioning systems face challenges in distributing heat between a refrigerant and a heat recovery unit, leading to reverse heating and increased compressor load, which can result in system failure due to differing specific heat capacities of water and refrigerant.
Innovation Solution
A heat ventilation and air conditioning unit with a controller that regulates refrigerant flow rates and pressures using 4-way valves and a one-way valve to maintain optimal heat distribution between the evaporator and heat recovery unit, preventing reverse heating and excessive compressor load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a portion of refrigerant is diverted from the evaporator to the water heater to recover heat, then heat recovery efficiency is improved, but the amount of heat accumulated in the water heating unit may exceed the heat of the refrigerant resulting in reverse heating of the refrigerant
Solution Approach 1:
The controller continuously monitors the temperature of refrigerant entering the compressor and adjusts the flow rate through the water heater accordingly. When the refrigerant temperature approaches a predetermined threshold, the controller reduces or stops the flow rate to prevent reverse heating, ensuring the system operates within safe parameters while maximizing heat recovery.
Solution Approach 2:
The system dynamically adjusts the refrigerant flow rate through the water heater based on real-time operating conditions. The controller modulates the flow rate to match the actual heat available from the refrigerant, preventing over-recovery that would cause reverse heating while maximizing energy utilization when conditions permit.
2Loss of energy
If heat is recovered from refrigerant in water heating unit, then energy efficiency is improved, but the temperature of refrigerant entering the compressor rises resulting in extra load on the compressor
Solution Approach 1:
The controller monitors refrigerant temperature and compressor operating conditions, adjusting the water heater flow rate to prevent excessive temperature rise that would overload the compressor. This feedback mechanism balances heat recovery benefits with compressor protection.
Solution Approach 2:
The system changes the flow rate parameter dynamically to optimize the balance between heat recovery and compressor load. By adjusting this parameter, the system maximizes energy efficiency while keeping the refrigerant temperature within safe operating limits for the compressor.
3Loss of energy
If the temperature of refrigerant increases beyond a limit, then heat recovery is maximized, but the intake pressure of the compressor exceeds a limit resulting in failure of the air conditioning unit
Solution Approach 1:
The controller takes preliminary action by monitoring refrigerant temperature and proactively adjusting the water heater flow rate before the refrigerant temperature can rise to dangerous levels. This preventive approach avoids compressor failure by maintaining safe operating parameters.
Solution Approach 2:
The system uses continuous temperature monitoring and feedback control to adjust the heat recovery process, preventing refrigerant temperature from exceeding safe limits that would cause compressor failure while still maximizing heat recovery within safe operating parameters.
4Loss of energy
If refrigerant flow rate to heat recovery unit is increased, then heat recovery efficiency is improved, but the heat distribution to the evaporator is reduced affecting space cooling/heating
Solution Approach 1:
The system dynamically adjusts the refrigerant flow rate to the water heater based on real-time demands for both heat recovery and space conditioning. This dynamic allocation optimizes the balance between recovering heat for water heating and maintaining adequate heat distribution for space cooling or heating requirements.
Solution Approach 2:
The controller applies partial action by adjusting the water heater flow rate to an optimal level that provides sufficient heat recovery without excessively reducing the heat available for space conditioning. This partial allocation ensures both functions operate effectively.
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 achieves ideal heat distribution, preventing reverse heating and maintaining compressor efficiency by controlling refrigerant temperatures and pressures, ensuring effective heating and cooling operations.
Implementation Method 1
a compressor adapted to compress a refrigerant to form a compressed refrigerant
Implementation Method 2
a condenser in fluid communication with the compressor to exchange heat between the compressed refrigerant and ambient air
Implementation Method 3
a first expansion device in fluid communication with the condenser to convert the condensed refrigerant into a cooled refrigerant
Implementation Method 4
an evaporator in fluid communication with the first expansion device to exchange heat between a space to be cooled and the cooled refrigerant
Implementation Method 5
a heat recovery unit in fluid communication with the compressor and the first expansion device to discharge heat of the condensed refrigerant to a medium
Data Source
Figure 1
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AI summary
A heat ventilation and air conditioning (HVAC) unit (100) is disclosed. The HVAC unit (100) includes a compressor (102), a condenser (104), a first expansion device (106), a second expansion device (118), a third expansion device (120), an evaporator (108), a heat recovery unit (110), a first 4-way valve (112), a second 4-way valve (114), a one-way valve (118) and a controller (124). The controller (124) determines a first discharge superheat temperature for the refrigerant entering the evaporator (108) and a second discharge superheat temperature for the refrigerant entering the heat recovery unit (110) and adjust the first flow rate and the second flow rate to maintain ideal heat distribution between the heat recovery unit (110) and the evaporator (108).