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Valeo Climate control is developing a software package for the design and simulation of car air-conditioning systems. This software package aims to improve Valeo's response to customer requirements concerning delays for design and sizing car air-conditioning systems performances and cost reduction. Further it shall help to capitalize our competence and expertise on the A/C systems. The comparisons between simulation and tests give a good level of accuracy. The software consists of three modules: A first module for car cabin thermal simulation in dynamic and stationary conditions. A second module for the determination and optimization of the A/C system components. A third module is under development for the dynamic simulation of the A/C system in non-standard operating conditions.

This paper presents the results of a study into an innovative system using a new type of technology for the automotive domain with the aim of improving passengers' thermal comfort. A study of the thermal interactions between the cabin and its passengers shows that radiative heat transfers clearly contribute to the passengers' thermal discomfort during the first few minutes of a vehicle's use. Therefore, to limit this kind of heat exchange, an innovative A/C system combining a conventional automotive A/C loop and a Heat Pipe Dashboard Panel has been developed. This reduces the dashboard temperature rapidly, immediately after starting the A/C system (70°C to 10°C in 3 min).

In order to reduce the fuel overconsumption, new air conditioning systems fitted with externally controlled compressors have been implemented. Their operating principle consists in driving electrically (external control) the compressor displacement in order to adjust the cooling capacity delivered by the A/C system to the cooling capacity required by the passenger compartment. Therefore, it is possible to reduce the mechanical power absorbed by the compressor and by this means, the fuel overconsumption. However, this potential of fuel consumption reduction can be only achieved under the condition that the other components of the A/C system, such as the thermostatic expansion valve (TxV), are well adapted all together in order to fully take advantage of the implementation of such new type of compressors. The paper describes the different possibilities of optimization of the TxV in regard to hunting phenomena.

Electrical Air Conditioning Systems for 42 V vehicles will provide many benefits in terms of Environment protection, car Architecture, cabin Comfort and overall Safety. E-A/C Systems essentially differ from conventional ones by the use of electrical compressors. First of all, they will be particularly well adapted to new powertrains, helping to make them more environmentally friendly. Accurate control and high efficiency under the most common thermal conditions will reduce the A/C impact on fuel consumption. Besides, higher sealing integrity will cut emissions of refrigerant during normal operation and maintenance. Secondly, the use of an electrically driven compressor (EDC) will suppress a belt, and will reduce the packaging constraints. This will help to design new vehicle architectures. Thirdly, the electrification of air conditioning will allow better thermal comfort. In particular, E-A/C Systems provide a good opportunity for cabin pre-conditioning.

The arising “Stop&Go” function contributes to the reduction of new cars fuel consumption. However, as the engine shuts off when the car stops, cabin heating and air conditioning cut off because they are belt driven. This paper first describes the cabin temperature evolution when it occurs. It shows that solutions must be found in order to guarantee passenger comfort maintaining. Different concepts are presented, built on fuel, electrical or thermal energy storage. A comparison is provided, showing that the latter should be preferred. The biggest remaining issue for long stops is storage itself.

Reduction of internal combustion engines fuel consumption is permanently researched. It leads automotive companies towards global energetic simulation tools to describe the interactions between the engine and the energy consumer systems. Valeo with the EMN Department of Energetic, develop a vehicle energy management tool. It will be able to describe the interactions between: engine, the car cabin heating system, electrical systems and other energy consumers (additional heating system, air conditioning system) implied in the vehicle operation. The first results given by the simulation model have approached quite accurately, the coolant loop warm-up curve, measured during a vehicle test in wind tunnel. The model solves the energy balance on the oil and coolant loops and computes: the heat flux from engine to coolant, the distribution of coolant flows in branches, the thermal exchanges involved in the heater core, the cooling radiator and the oil cooler.

Experiments were conducted on laminate evaporator to determine the effect of the tank position on the evaporator heat transfer and pressure drop. The experiments were conducted on the evaporator calorimeter facility that is fully instrumented per ASHRAE specifications. A typical 4 pass laminate evaporator was used for testing. The refrigerant used for this investigation was R-134a. An oil circulation ratio of 2% was used for this study. The test conditions were: air inlet state was maintained at 27°C of dry bulb temp and 50% RH; average condensing and evaporation pressures were maintained at 15.5 & 1.96 kg/cm2 G, respectively with 5°C evaporator superheat and 5°C condenser subcooling; and air flow rate was varied from 120 to 480 m3/hr. The result shows that there is a significant impact of the tank position on the evaporator heat transfer rate and pressure drop.

This paper presents the results of a study of the various thermal interactions between the automotive passenger compartment and the passengers, using the equivalent temperature concept. Radiative and convective heat exchanges are described. A technical proposal to improve the thermal comfort of passengers is also made.

Expanding the temporal scope of air conditioning in cars is an important customer expectation. It must be available when the engine is off for climate control purposes (during “stop&start” operations or short parking) or for thermal comfort preparation (cabin pre-cooling). Different technical solutions can be classified according to the kind of energy storage they are based on. Regarding stop&start, many solutions are possible. The selection should be made in accordance with the hybridisation level of the vehicle. For parking cooling and pre-cooling, weight is the main issue. Thermal storage or electrical batteries can be used, but tens of kilograms are required. Auxiliary power units would be necessary to obtain full comfort in these conditions.

The paper deals with an innovative system using a new type of technology for the automotive domain in order to improve rear passengers’ thermal comfort. This device is an add-on thermal module plugged into the headliner of a car. This kind of product has been developed and integrated in a car for validation. Tests have been performed in terms of thermal comfort improvement using a human panel. They show a real effect at the head level of the rear passengers in summer and in winter. Moreover, it offers independent control to the left and right rear passengers in terms of mass flow and temperature with easier in-vehicle integration for the car makers than a rear HVAC.

The thermochemical energy storage could be a suitable solution for heating and air conditioning electric vehicles. This paper gives the results of a preliminary study engaged to test the STELF process using the metallic chloride/ammonia couple. Among the large number of solid/gas couples available, the MnCl2/NH3 couple features an energy storage capacity of about 180 Wh and 90 Wh per kg of reactive and answers to an automotive application temperature respectively for the heating and the cooling. In winter, the reactor can provide heating to warm the passenger compartment but also to the outer evaporator heat exchanger to avoid the icing up phenomenon. Simulations show the thermodynamic feasibility of the process in the heating, cooling and regeneration modes in order to warm up, air condition and preheat respectively the electric car passenger compartment.

The paper presents the VALEO and RENAULT approach to study odor problems for passengers compartment. The first part describes the method chosen to form a panel, and the second part presents a vehicle application.

This paper presents an experimental investigation of two passive thermal preconditioning technologies, pre-ventilation and solar shields, and a combination of both. A Design of Experiment (DOE) was defined in order to evaluate the influence of several parameters (air mass flow and air diffusion mode, size of the air extractors, location and type of solar shield) on the passengers' thermal comfort on entry into the car cabin and after a short A/C running time (10 min). Results show that solar shields are more efficient than pre-ventilation, which means that radiative heat transfers are more effective than the convective heat transfers, even with high air flows. The type of solar shields together with their location on the windows is also influential. After preconditioning, 10 minutes of air conditioning might reduce the air temperature at face level of the front passengers, compared to a non preconditioned car cabin.

Current systems of air diffusion inside the car cabin are leading in some conditions to passenger discomfort. To solve this problem our company has developed a new concept of air diffusion. It consists in an air distribution system composed of a wide central air diffusion area on the top of the instrument panel and two lateral outlets. To evaluate the comfort performances of the concept a methodology based on experiments, simulation and subjective evaluation has been defined and used. The comparison between the current air diffusion and the new one shows a significant impact on the driver's and passenger's comfort. The purpose of this paper is to describe the methodology developed to analyze the air diffusion impact on the comfort and the improvements obtained by the new concept.

This paper describes the development of our software simulation of the car cabin and its air conditioning system. The validation of this software requires a lot of experimental data ( test bench and wind tunnel). The models of this software are based on a physical and parametrical approach. This paper also details the comparison between test and simulation in different operating conditions both the car cabin and the A/C systems. The result obtained from simulation give a good level of accuracy.

One of the main issue for the development of current automotive air conditioning systems concerns the reduction of the fuel consumption resulting from the A/C absorbed power. This fuel use reduction can be for one part obtained by the means of an A/C systems energetic efficiency improvement. Different technical solutions can be implemented. One of these techniques consists in the optimization, or even the control of the refrigerant subcooling at the outlet of the condenser.

Textron Automotive Trim, Valeo Climate Control, and Torrington Research Company, with assistance from GE Plastics, have developed an integrated instrument panel system to meet ever-increasing industry targets for: Investment and piece-cost reduction; Mass/weight savings; Quality and performance improvements; Packaging and space availability; Government regulation levels; and Innovative technology. This system, developed through feedback with the DaimlerChrysler Corporation, combines the distinctive requirements of the instrument panel (IP) with the heater-ventilation-air-conditioning (HVAC) assembly. Implementing development disciplines such as benchmarking, brainstorming, and force ranking, a number of concepts were generated and evaluated. Using a current-production, small, multi-purpose vehicle environment, a mainstream concept was designed and engineered.

Performance of a laminate (plate type) evaporator is simulated by using hydrocarbons as the alternative refrigerants. The performance of the evaporator is simulated with Propane (R-290), Isobutane (R-600a), and 50/50 mixture (by weight) of Propane and Isobutane. The performance is compared to a system with R-134a as the working fluid. For a given cooling capacity, the refrigerant mass flow rates for hydrocarbon refrigerants are significantly lower than R-134a. However, the heat transfer coefficients are comparable in magnitudes to the base case (R-134a) which results in heat transfer rates that are very close to that of the base case. Hence, the simulated rate of heat transfer for hydrocarbon refrigerants is very close (within -3.5%) to that of R-134a system. From experiment's point of view the rate of heat transfer are same for all 4 refrigerants. The simulated thermal performance has been compared with the experimental test data obtained from the system bench.

Performance of a parallel flow condenser is simulated by using hydrocarbons as the alternative refrigerants. The performance of the condenser is simulated with Propane (R-290), Isobutane (R-600a), and 50/50 mixture (by weight) of Propane and Isobutane. The performance is compared to a system with R-134a as the working fluid. For a given condenser heat rejection capacity, the refrigerant mass flow rates for hydrocarbon refrigerants are significantly lower than R-134a. However, the heat transfer coefficients are comparable in magnitudes to the base case (R-134a) which results in heat transfer rates that are very close to that of the base case. Hence, the simulated rate of heat transfer for hydrocarbon refrigerants is very close (within ±3%) to that of R-134a system. The pressure drop for hydrocarbon refrigerants are significantly lower in comparison to R-134a. The simulated thermal performance has been compared with the experimental test data obtained from the system bench.