Concentric HVAC Fan and Heat Exchanger for Compact Cab Cooling
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Solution Overview
Problem
Agricultural vehicle cabs with large glass surfaces experience significant solar heat loads, leading to inefficient air conditioning systems that are bulky and often resort to spot cooling, which can result in uneven temperature distribution within the cab.
Innovation Solution
A compact roof-enclosed HVAC system with a concentrically arranged fan unit, evaporator unit, and heater unit, utilizing an annular impeller driven by a single motor to enhance air flow and heat transfer efficiency, allowing for uniform cooling of the entire operator station.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If large heat rejection capacity is used to handle solar heat loads, then cooling capacity is improved, but system size increases making it difficult to fit in the vehicle
Solution Approach 1:
The evaporator core is positioned inside the fan housing, and the heater core is positioned inside the evaporator core, creating a nested concentric arrangement. This nesting principle allows multiple heat exchanger cores to occupy the same spatial envelope, achieving high heat rejection capacity in a compact package that can be mounted in the limited roof space between the upper and lower roof panels.
Solution Approach 2:
The patent transitions from traditional linear heat exchanger arrangements to a three-dimensional concentric cylindrical configuration. The fan housing forms an outer cylinder, the evaporator core forms a middle cylinder, and the heater core forms an inner cylinder. This dimensional reorganization maximizes heat transfer surface area within the constrained vertical space between roof panels.
2Volume of stationary object
If long thin heat exchanger cores are used to minimize packaging impact, then system size is reduced, but heat transfer efficiency decreases due to poor aspect ratio
Solution Approach 1:
The patent employs curved cylindrical surfaces for all heat exchanger cores and the fan housing. The evaporator core and heater core are both cylindrical structures with curved surfaces optimized for heat transfer. This curvature provides superior heat transfer characteristics compared to flat plate configurations, while the concentric arrangement ensures uniform air flow distribution across the entire heat transfer surface area.
Solution Approach 2:
The patent changes the geometric parameters of the heat exchanger cores from traditional linear configurations to concentric cylindrical forms with specific diameter ratios. The evaporator core has a first diameter and the heater core has a second diameter, creating optimized aspect ratios that maximize heat transfer efficiency. The curved surface area to volume ratio is enhanced through this concentric cylindrical geometry.
3Volume of stationary object
If spot cooling is used to reduce system size, then HVAC system capacity is reduced, but uniform cooling of the entire cab is compromised
Solution Approach 1:
The concentric heat exchanger configuration serves multiple functions simultaneously: the evaporator core provides primary cooling, the heater core provides heating capability, and both cores work together to condition air for distribution throughout the entire cab. This multi-functional design eliminates the need for separate spot cooling systems while providing uniform temperature control across the whole operator compartment.
Solution Approach 2:
The HVAC system pre-cools or pre-heats air in the concentric heat exchanger cores before distribution. The fan housing draws ambient air through the evaporator core first, then through the heater core, ensuring the air is properly conditioned before being blown into the cab. This preliminary conditioning action ensures uniform temperature distribution throughout the entire cab space rather than localized spot cooling.
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 solution provides a high heat rejection capacity in a compact package, enabling efficient and uniform cooling of the entire cab while minimizing space requirements and preventing overheating or undercooling.
Implementation Method 1
The blades force air radially outwardly upon rotation of the fan unit
Implementation Method 2
make heat transfer to the air flowing through them difficult to uniformly transfer heat between the air and the entire face area of the core
Data Source
AI summary
There is a need for a compact and high capacity HVAC system for a vehicle cab. This need is met by a roof enclosed HVAC system. The system includes a roof upper panel, a roof lower panel, a fresh air duct communicated with a fresh air inlet exposed to an exterior of the cab, a recirculation air duct communicated with a recirculation air inlet exposed to an interior of the cab, and a conditioned air duct communicated with an air outlet exposed to the interior of the cab. An HVAC unit is mounted between the roof upper and lower panels. The HVAC unit includes a fan unit, a heater unit and an evaporator unit. The heater and evaporator units are concentrically arranged around and surrounding the fan unit. The fan unit draws air from the fresh air duct and the recirculation air duct and blows air through the heater unit and an evaporator unit and into conditioned air ducts