Heat Pump Water Heater Condenser Nesting for Compact Heat Transfer
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Solution Overview
Problem
Tank-type heat pump water heaters with internal condensers face challenges in achieving high heat transfer efficiency while maintaining a compact design, as longer condensers are needed for efficiency but reduce storage volume and require more refrigerant, while shorter condensers compromise on efficiency.
Innovation Solution
A water heater design featuring a thermosiphon tube surrounding a condenser tube within the tank, with a heat pump system that includes an evaporator, compressor, expansion device, and condenser, allowing for forced water flow through a water flow channel between the thermosiphon and condenser tubes to enhance heat transfer and deliver heated water efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the condenser tube is made longer to improve heat transfer efficiency, then heat transfer efficiency is improved, but storage volume is reduced and refrigerant charge increases
Solution Approach 1:
The condenser tube is nested inside the thermosiphon tube, creating a concentric heat exchanger arrangement. This allows the condenser to be positioned vertically through the water tank without occupying horizontal storage space, thereby maintaining storage volume while achieving the necessary heat transfer surface area through increased vertical length
Solution Approach 2:
The condenser tube transitions from a horizontal or external arrangement to a vertical orientation within the tank, utilizing the vertical dimension for heat transfer. This dimensional change allows the condenser to extend through the water column, improving heat transfer efficiency without compromising the tank's storage capacity
2Loss of energy
If the condenser tube is made longer to improve heat transfer efficiency, then heat transfer efficiency is improved, but refrigerant charge increases
Solution Approach 1:
By nesting the condenser tube within the thermosiphon tube, the design achieves a compact configuration that maximizes heat transfer surface area within a confined space, reducing the total length of refrigerant piping required and thereby decreasing the refrigerant charge needed while maintaining heat transfer efficiency
3Volume of stationary object
If the condenser tube is made shorter to reduce refrigerant charge and storage volume reduction, then storage volume is maintained and refrigerant charge decreases, but heat transfer efficiency is reduced
Solution Approach 1:
The heat transfer function is segmented between the condenser tube and the thermosiphon tube, with the thermosiphon tube acting as an extended heat transfer surface. This segmentation allows the system to achieve adequate heat transfer efficiency with a shorter condenser tube by utilizing the thermosiphon tube's surface area for additional heat exchange
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 improves heat transfer efficiency, reduces the need for lengthy condenser tubes, decreases refrigerant charge, and maintains efficient operation by delivering heated water directly to the top portion of the tank, thereby enhancing overall performance and reducing material costs.
Implementation Method 1
the condenser tube being at an elevated temperature compared to water temperature in the water flow channel due to the refrigerant cycle; heating water within the water flow channel via an exchange of heat from the condenser tube
Implementation Method 2
a thermosiphon tube in the water tank and having a first end in a bottom portion of the water tank and a second end in a top portion of the water tank
Data Source
AI summary
A water heater includes a water tank for storing water to be heated and a thermosiphon tube in the water tank. The thermosiphon tube has a first end in a bottom portion of the water tank and a second end in a top portion of the water tank. At least a portion of a condenser tube of a heat pump is surrounded by the thermosiphon tube to define a water flow channel between the thermosiphon tube and the condenser tube. The condenser tube is at an elevated temperature compared to water temperature in the water flow channel due to a refrigerant cycle of the heat pump. A water pump is configured to flow water through the water flow channel to heat the water in the water flow channel and deliver the heated water into the top portion of the water tank through the second end of the thermosiphon tube.