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Technical Paper

An Innovative Thermal Dashboard System

2004-03-08
2004-01-1383
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).
Technical Paper

Experimental Investigation to Determine The Effect of Laminated Evaporator's Tank Position on Heat Transfer and Pressure Drop

2002-03-04
2002-01-1029
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.
Technical Paper

Experimental Investigation of a Thermal Preconditioning of a Car cabin

2005-05-10
2005-01-2057
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.
Technical Paper

Influence of Various Heat Transfers on Passenger Thermal Comfort

2003-03-03
2003-01-1075
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.
Technical Paper

Performance Prediction of a Laminate Evaporator with Hydrocarbon Refrigerants as the Working fluids

2001-03-05
2001-01-1251
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.
Technical Paper

Simulating Performance of a Parallel Flow Condenser Using Hydrocarbons as the Working Fluids

2001-05-14
2001-01-1744
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.
Technical Paper

Thermal Energy Storage System by Solid Absorption for Electric Automobile Heating and Air-Conditioning

1995-02-01
950017
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.
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