Short-Cycle Heat Pump Defrosting for Frost and Peak Load Control
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Solution Overview
Problem
Air-source heat pump systems face inefficiencies and high operational costs due to frost/ice buildup on exterior heat exchangers during cold temperatures, leading to compressor stress, charge imbalances, and peak electrical demand, as existing defrost methods are either costly or inefficient, causing heat loss and peaking concerns for utility companies.
Innovation Solution
A defrost system that includes a specially designed refrigerant transport tubing, a supplemental hot gas line, and controlled valve operations to frequently and briefly direct hot refrigerant gas to the exterior heat exchanger, along with a restriction in the vapor line, to mitigate frost/ice buildup while maintaining efficient heat supply and reducing compressor stress and peak power usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional defrost cycles are used to melt frost/ice on exterior heat exchangers, then frost removal is achieved, but compressor stress increases and peak electrical demand occurs
Solution Approach 1:
The patent implements frequent short-cycle defrost operations where the reversing valve is activated periodically for brief durations (e.g., 10-30 seconds) rather than allowing frost to accumulate and then performing long defrost cycles. This periodic action prevents significant frost buildup while avoiding the sustained compressor stress and peak electrical demand associated with conventional defrost cycles
Solution Approach 2:
The system performs preliminary defrost actions by frequently activating the reversing valve before frost/ice can significantly impede heat exchanger performance. This preventive approach maintains operational efficiency without requiring intensive defrost operations that would stress the compressor and create peak electrical demand
2Object-affected harmful factors
If conventional defrost cycles are used to remove frost/ice, then frost removal is achieved, but heat loss increases and operational efficiency decreases
Solution Approach 1:
By implementing frequent short-cycle defrost operations, the system maintains near-continuous heating operation rather than interrupting for extended defrost periods. The brief reversing valve activations (10-30 seconds) are insufficient to significantly reduce heating output, thereby minimizing heat loss while still preventing frost accumulation that would otherwise impair heat exchange efficiency
3Object-affected harmful factors
If conventional defrost cycles are used, then frost removal is achieved, but peak electrical demand increases creating utility peaking concerns
Solution Approach 1:
The frequent short-cycle defrost approach distributes the electrical load of defrost operations across many brief intervals rather than concentrating it in single long-duration events. This periodic distribution of small power demands avoids creating peak electrical demand that would concern utility companies, while still effectively preventing frost buildup through cumulative defrost action
4Productivity
If frequent short-cycle defrost operations are implemented, then frost buildup is prevented and operational efficiency is maintained, but system complexity increases due to additional control mechanisms
Solution Approach 1:
The system utilizes the existing reversing valve and control infrastructure already present in heat pump systems to implement frequent short-cycle defrost operations. By leveraging existing components rather than introducing entirely new control mechanisms, the patent achieves improved operational efficiency through frequent defrost cycling while minimizing the increase in system complexity
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 solution effectively prevents significant frost/ice buildup, maintains operational efficiency, reduces compressor stress, and minimizes peak electrical demand, ensuring continuous heat supply and lowering energy costs for both users and utility companies.
Implementation Method 1
hot refrigerant gas...into the refrigerant transport tubing of the exterior air-source heat pump system...effectively prevents significant frost/ice buildup
Implementation Method 2
a restriction in the vapor line...controlled valve operations to frequently and briefly direct hot refrigerant gas
Data Source
AI summary
A heat pump system is configured to have a defrost cycle operable during a heating mode of operation. The system uses: larger than conventionally sized capillary tubes at the liquid refrigerant entry end of an exterior air-source heat exchanger; a special amount of additional refrigerant charge; a supplemental hot gas refrigerant transport line extending from the compressor; a special valve in the new supplemental hot gas refrigerant transport line; and another special valve controlling a restriction to the refrigerant flow in the common consolidated vapor refrigerant transport line exiting the exterior heat exchanger. A controller opens the valve in the new supplemental hot gas refrigerant transport line and to simultaneously engages, for a special period of time, the valve controlling the specially sized restriction to the refrigerant flow in the common consolidated vapor refrigerant transport line exiting the exterior heat exchanger at periodic intervals during potential frost conditions. Additionally, the exterior heat exchanger fan is disabled during a part of the defrost cycle.