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In the modern era of automotive industry, occupant comfort inside the cabin is a basic need and no more a luxury feature. With increase in number of vehicles, the expectations from customers are also changing. One of the major expectations from real world customers is quick cabin cooling thru all seasons, particularly when the vehicle is hot soaked and being used in summer conditions. Occupant thermal comfort inside the vehicle cabin is provisioned by a mobile air conditioning (MAC) system, which operates on a vapor compression-based cycle using a refrigerant. The main components of a direct expansion (DX) based MAC system are, a compressor, condenser, evaporator, and expansion valve. Conditioned air is circulated inside the cabin using a blower, duct system and air vents. The AC condenser is the most critical component in AC circuit as it rejects heat, thereby providing for a cooling effect inside the cabin.

AC system provides the human comfort inside the cabin of a vehicle but at the expense of consumption of energy from the vehicle. On a global perspective for the bus segment, there is an increased demand for cooling in tropical countries. Optimization needs to be done in existing AC systems w.r.t packaging, cost & performance constraints. Major elements contributing to heat ingress are engine hood, front firewall, windshield & side glasses and bus body parts. Due to these reasons inadequate passenger comfort and poor cool down performance of the vehicle is observed. This paper refers to the reduction of heat ingress through different DOE (Design of Experiment) in the area of design & validation for duct & vent layout, insulation, glass & paint technology, evaporator blowers. The new duct design has been evaluated using a CFD tool by varying various parameters to generate desired output. The integrated use of the modifications was found significant improvement at vehicle level.

HVAC system design has an accountability towards acoustic comfort of passengers of a vehicle. Owing to larger cabin volume of a bus, multiple air blowers have to be installed to ensure comfort of passengers. Such multiple blowers produce significant flow induced noise inside the cabin. For commercial success, it becomes essential to predict intensity of such a flow induced noise at very early stages in product development. Conventionally sliding mesh based CFD approach is deployed to predict flow and turbulence noise around each blower. However due to complexity, this method becomes computationally intensive resulting in cost and time inefficiency. Hence it is desirable to innovate around an alternative rapid, reliable prediction method, which ensures quick turnaround of prediction.

Electric radiator fan is a vital component within IC and EV passenger vehicle cooling system. However, due to its operation, it induces noise and in-cab vibration affecting human comfort level. This paper primarily focus on FMS (Fan Motor Shroud) assembly induced steering wheel vibrations in a vehicle under idle + AC ON condition. The entire NVH performance was cascaded from vehicle level to component level to evaluate for high steering wheel vibration and its transfer path analysis. Unit level vibrations study was also carried out using a rigid rig under controlled conditions. Based on FMS vibration analysis, it was observed that fan blade rotating imbalance leads the high vibrations within system. Thus, a balancing method with higher precision and accuracy was used to measure and balance the fan under all operating conditions. Sensitivity analysis had been carried out for fan imbalanced boundary conditions and operating speeds.

Transmission of vibration and noise to the occupants and especially driver contributes significantly to the quality perception of the motor vehicle and eventually, it affects the overall ride comfort. These forces mainly reach to customer through tactile locations, i.e. floor, gearshift lever, steering wheel and seat. Showroom/Parking customer drive pattern of a vehicle evinces the steering system and driver’s seat rail vibration as strikingly linked aspect to evaluate human comfort [1]. This paper deals with the study of vibration at steering wheel and seat affecting human comfort at engine idle rpm with AC ON and OFF condition for passenger vehicles. The transmissibility of engine and radiator induced vibrations has been investigated with respect to modal alignment of steering and seat system.

The automotive application places very special demands on the air conditioning system. As is the case with any other process, system efficiency is very important and the automotive air-conditioning application is no exception. While the characteristics of all the major components in the air conditioning system like compressor, condenser, evaporator and blower contribute to overall system efficiency, localized inefficiencies do play a part and so must be kept to a minimum, especially in this day and age when extra emphasis is being laid on sustainability. One such phenomenon that contributes to the system inefficiency is heat pick-up in suction line. Since the temperature at the evaporator-outlet is quite lower than ambient and also its surroundings (steering system pipes and hoses, engine, air intake pipes and so on), the refrigerant picks up heat as it moves along the suction line up to the compressor inlet. This heat pick-up is detrimental to the overall system performance.

In an automotive air conditioning system, evaporator is well designed for effective heat transfer between refrigerant and air flowing over the evaporator. This cold and dehumidified air obtained at evaporator is then supplied to passenger cabin. There are various parameters like air flow over evaporator, ambient temperature, humidity condition and condensate drain mechanism which can cause frost formation over the evaporator core. This study presents the probable causes of frost formation and their effects on the performance of evaporator and thus affecting overall performances of the automotive air conditioning system. In this study effect of variation in four major independent factors such as poor response of thermistor, undercharged refrigerant system and overcharged refrigerant system, drop in air flow by blower due to clogged air-filter, and also the effect of type of compressor has been studied.

The engine compartment of passenger car application contains various source which radiates the produced heat and raises the temperature level of the compartment. The rise in compartment temperature increases the body temperature of individual component. The rise in body temperature of critical components can endanger the durability or functionality of the specific component or a system in which it operates. The aim of this paper is to strategize thermal protection of the rear mounted engine and its components of a vehicle having radiator and cooling fan mounted in front. An additional ventilation fan with speed sensor is fitted alongside rear mounted engine and a unique monitoring technique framed in the EMS ECU to protect critical components like HT cables, alternators, ECUs, wiring harness etc. from thermal damage. The EMS continuously monitors the engine speed, vehicle speed and the PWM signal of ventilation fan to ensure the intended operation of the ventilation fan.

Ever tightening emission limits and constant pressure for increasing engine power are resulting in increased engine operating temperature. This coupled with continuous drive for fuel economy improvement because of the stiff competition are forcing OEMs to explore alternative cooling solutions resulting in less power take off and quick response as cooling requirement shoots up. Aim of this paper is to analyze the relative benefits of incorporating a new cooling fan drive system concept over conventional viscous fan driven cooling system with step-less variable speed control independent of engine speed variation. Hydraulic fan drive system control fan rpm based on the fluid temperature as compared to air temperature in viscous coupling fan drive system. HFD system provides quick response when increase in coolant temperature is observed. HFD system in this way provide more control on fan rpm.

In small car segment, as far as hybridization is concerned, the space and safety constraint demands use of lower voltage viz., 48 V as compared to >100-volt-systems used for vehicles in other segments. These systems also have advantage of reduced copper weight due to reduced current. As 12 V systems are replaced by the 48 V systems, the auxiliary 12 V loads would necessitate implementation of a DC-DC converter. Considering the requirements of auxiliary loads that are fed from 12 V battery, the power rating of the DC-DC converter can get considerably high resulting in increased size. Hence, it is advisable to re-design at least some of the 12 V auxiliary systems to 48 V such as the radiator fan motor. This, along with the issues faced in the existing PMDC Motor with regard to efficiency and sizing have generated interest to investigate better alternatives for the motor.