Heat Pump Water Heater Preheating for Cold-Climate Operation
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Solution Overview
Problem
Conventional heat pump water heaters are limited by their inability to operate effectively in cold temperatures and are inefficient due to scale buildup, which reduces their energy efficiency and requires a backup electric heater.
Innovation Solution
An energy-efficient heat pump system with an evaporator coil and a heater associated with it to maintain a temperature differential and prevent scale buildup, using a refrigerant flow circuit and a plasma pulse spark system to enhance heat transfer and prevent fouling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional HPWH operates in cold temperature climates, then heat transfer to hot water tank is insufficient, but adding backup electric heater increases energy consumption
Solution Approach 1:
The system performs preliminary heating of the environmental medium (air) before it contacts the evaporator coil. By pre-heating the air using a portion of the condenser output or other heat sources, the system ensures sufficient temperature differential for effective heat transfer even in cold climates, preventing the need for backup heating
Solution Approach 2:
The patent introduces an intermediate heating stage where the environmental medium is heated by a pre-heater device before entering the evaporator. This intermediary step allows the system to maintain effective heat transfer in cold temperatures without requiring the backup electric heater to directly heat the water tank
2Reliability
If scale accumulates on HPWH surfaces, then heat transfer coefficient decreases by 50-80%, but swirling water does not substantially mitigate scaling
Solution Approach 1:
The system employs vibration mechanisms that create mechanical disturbances in the water flow and on heat transfer surfaces. This vibration prevents scale accumulation by disrupting the deposition process and keeping surfaces cleaner, thereby maintaining higher heat transfer coefficients over time
Solution Approach 2:
The patent utilizes changes in flow parameters (velocity, turbulence) and thermal parameters to prevent scale formation. By dynamically adjusting flow conditions and introducing controlled disturbances, the system prevents the steady-state conditions that lead to scale accumulation
3Temperature
If evaporator pressure falls below 5 bars in winter, then condenser pressure drops to 19 bars with saturation temperature of 49°C, but maximum hot water temperature achieved is only 40°C
Solution Approach 1:
The system pre-heats the environmental medium before it contacts the evaporator, which maintains higher evaporator pressures by improving the temperature differential for heat absorption. This preliminary heating action prevents the pressure drop that would otherwise occur in winter conditions
Solution Approach 2:
The patent employs parameter changes in the refrigerant cycle by adjusting operating pressures and temperatures through controlled heating of the air supply to the evaporator. This maintains the refrigerant in optimal pressure ranges for efficient heat transfer and adequate hot water temperature production
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 operates efficiently in extreme temperatures, maintaining high energy efficiency and preventing scale buildup, achieving a coefficient of performance of at least 2.2 and up to 350% energy generation per unit consumed.
Implementation Method 1
A heater is operatively associated with the evaporator for heating an environmental medium prior to the environmental medium contacting the evaporator coil
Implementation Method 2
The electricity consumed by these HPWH's is used to transfer heat rather than to generate heat
Implementation Method 3
The schematic diagrams of FIGS. 1(a)-1(b) illustrate why conventional HPWH's are unable to provide a sufficient amount of heat
Implementation Method 4
The condenser temperature of the HPWH shown in FIG. 1(a) during the spring, summer and fall seasons reaches about 21 bars, which is sufficient to produce hot water
Implementation Method 5
The evaporator pressure falls below 5 bars due to a decrease in the temperature differential between the temperature of the surrounding environment and the temperature of the refrigerant
Data Source
AI summary
An energy efficient heat pump system capable of operating in extreme low and high temperature environments. The heat pump system includes an evaporator, a heater operatively associated with the evaporator, compressor and condenser. In an exemplary embodiment, the heat pump system may further include a plasma pulse-spark system to facilitate removal of scale deposits. The heater heats an environmental medium prior to the environmental medium exchanging energy with a refrigerant located in an evaporator coil of the evaporator in order to maintain a predetermined minimum temperature differential between the environmental medium when it contacts the evaporator coil and the refrigerant when located in the evaporator coil. The system allows efficient operation at low temperatures.