Air-conditioning device for a compartment, in particular for a railway vehicle, and method for defrosting the device
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Solution Overview
Problem
Existing air conditioning systems for railway vehicles face performance degradation due to frost accumulation on external heat exchangers, leading to reduced thermal comfort and increased energy consumption when defrosting, as they often require electric heating or oversized components.
Innovation Solution
The system employs two independent heat pump circuits connected to a thermal storage tank, allowing defrosting of the external heat exchanger by drawing heat from the tank without compromising compartment heating, thus maintaining thermal comfort without electric heating and avoiding oversized components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the heat pump circuit reverses the cycle to defrost the second heat exchanger, then the frost is melted, but the thermal comfort inside the compartment decreases due to heat removal
Solution Approach 1:
The system divides the heat pump functionality into two independent circuits (primary and secondary), each capable of independent operation. This segmentation allows one circuit to perform defrosting while the other maintains compartment heating, resolving the contradiction between defrosting effectiveness and thermal comfort maintenance.
Solution Approach 2:
The invention introduces a thermal storage tank as an intermediary heat source for defrosting. Instead of directly extracting heat from the compartment air, the system uses stored thermal energy from the tank, which acts as a buffer between the defrosting process and the compartment environment, thereby maintaining thermal comfort.
2Temperature
If an electric heater is activated to compensate for heat removal during defrosting, then the compartment temperature is maintained, but energy consumption increases
Solution Approach 1:
The system uses its own stored thermal energy to compensate for heat removal during defrosting, rather than relying on external electric heating. The thermal storage tank provides the necessary heat independently, making the system self-sufficient and avoiding additional energy consumption from external sources.
Solution Approach 2:
The system recovers and stores excess thermal energy during periods when heating demand is low, then utilizes this stored energy during defrosting operations. This approach replaces the need for energy-intensive electric heating by recycling previously captured thermal energy.
3Temperature
If a thermal storage tank is used for defrosting, then compartment heating is maintained, but the device requires oversized components
Solution Approach 1:
By dividing the heating system into two independent heat pump circuits, each circuit can be sized for partial heating capacity rather than full capacity. This segmentation allows the use of a smaller thermal storage tank and smaller heat exchanger components while still maintaining adequate heating performance through coordinated operation of both circuits.
4Reliability
If frost accumulates on the second heat exchanger, then heat exchange performance decreases, but the system structure remains simple
Solution Approach 1:
The system performs preliminary defrosting operations using the thermal storage tank before frost accumulation significantly degrades heat exchange performance. The stored thermal energy is readily available to melt frost promptly, preventing performance degradation without requiring complex real-time monitoring or response systems.
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 defrosts the external heat exchanger without reducing compartment thermal comfort and reduces energy consumption by utilizing stored heat, enhancing operational efficiency and flexibility.
Implementation Method 1
a thermal storage tank (46) connected to the primary heat pump circuit (12), in parallel with said first primary heat exchanger (14)
Implementation Method 2
the refrigerant takes heat from the first heat exchanger, and brings the heat to the second heat exchanger in a manner to melt the frost
Implementation Method 3
brings the heat to the second heat exchanger in a manner to melt the frost
Implementation Method 4
exchanges heat, on the one hand with the air of the compartment in the first heat exchanger, and on the other hand with the outside air in the second heat exchanger
Implementation Method 5
each heat exchanger comprises fins increasing the exchange surface with the air
Implementation Method 6
a compressor (16), a second primary heat exchanger (18) with outside air
Data Source
Figure 1
AI summary
The air conditioning unit (10) includes a primary heat pump circuit (12), comprising a first primary heat exchanger (14) with the compartment air, a primary compressor (16), a second primary heat exchanger (18) with outside air, and a primary expansion device (20), and a thermal storage tank (46) connected to the primary circuit (12) in parallel with said first primary heat exchanger (14) with the compartment air. The air conditioning unit (10) includes a secondary heat pump circuit (12'), comprising a first secondary heat exchanger (14') with the compartment air, a secondary compressor (16'), a second secondary heat exchanger (18') with outside air, and a secondary expansion device (20'). The thermal storage tank (46) is connected to the secondary circuit (12') in parallel with said first secondary heat exchanger (14') with the compartment air.