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Practical Approach to Develop Low Cost, Energy Efficient Cabin Heating for Extreme Cold Operating Environment
Abstract:
In cold climatic regions (25°C below zero) thermal comfort
inside vehicle cabin plays a vital role for safety of driver and
crew members. This comfortable and safe environment can be achieved
either by utilizing available heat of engine coolant in conjunction
with optimized in cab air circulation or by deploying more costly
options such as auxiliary heaters, e.g., Fuel Fired, Positive
Temperature Coefficient heaters.
The typical vehicle cabin heating system effectiveness depends
on optimized warm/hot air discharge through instrument panel and
foot vents, air directivity to occupant's chest and foot zones
and overall air flow distribution inside the vehicle cabin. On
engine side it depends on engine coolant warm up and flow rate,
coolant pipe routing, coolant leakage through engine thermostat and
heater core construction and capacity.
The purpose of this study is to evaluate a conventional coolant
type heating system and enhance its capacity to warm the vehicle
cabin up to comfortable temperatures of +10°C to +15°C in head zone
and +15°C to +20°C in foot zones of occupants. These temperatures
are to be achieved in 15 minutes after vehicle start, prior to
which vehicle has been cold soaked for 10 hours at ambient
temperature of 25°C below zero.
A series of experiments have been carried out on a conventional
coolant type automotive cabin heating system on a test bench to
optimize the split of warm air hitting driver and occupant's
chest and leg zone. Further optimization is carried out on
directivity and velocities of warm air impinging on target zones
such as upper and lower body of occupants.
Once parameters critical to performance as mentioned above are
optimized on a bench, the heating system is mounted inside a
vehicle cabin. To improve overall heating effectiveness hot air
leakage paths from the vehicle cabin have been identified by using
a simple test rig and these paths were closed using grommets and
sealant. The vehicle is tested in a cold climatic chamber at 25°C
below zero. This trial is conducted on a chassis dynamometer to
simulate actual road load conditions. In this phase it is observed
that the criteria for thermal comfort are met with the conventional
coolant type heating system.
This practical approach to meet thermal comfort requirements at
extreme cold conditions, avoids the use of costly and complex
auxiliary cabin heaters, which would have led to increase in energy
consumption and environment pollution.