Compact HVAC system for a motor vehicle

Abstract

The invention relates to a compact vehicle HVAC system including an evaporator unit, a condenser unit, and a component unit, as well as a refrigerant circuit. The evaporator unit and the condenser unit each are provided with air-passed heat exchangers and a fan in a casing. Further circuit components are displaced within the component unit. The casings of the evaporator unit, the condenser unit, and the component unit advantageously establish a connected compact casing arrangement. The heat exchangers are displaced within the compact casing arrangement. The refrigerant circuit is established for a combined refrigeration plant and heat pump operation as well as an afterheating operation, whereby in the afterheating operational mode the heating power of the afterheater established as condenser / gas cooler and the cooling power of the evaporator are controllable independently of each other.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This application claims priority to German Patent Application Serial Number DE 10 2009 028 522.9 filed Aug. 13, 2009, the entire disclosure of which is hereby incorporated herein by reference.FIELD OF THE INVENTION[0002]The invention relates to a compact vehicle HVAC system including different units. The units establish a connected, compact casing arrangement. The compact vehicle HVAC system is provided for the combined refrigeration plant and heat pump operation as well as an afterheating operation for heating, cooling and dehumidifying of the air to be conditioned for the passenger compartment. Also, the invention relates to a process for operating the HVAC system.BACKGROUND OF THE INVENTION[0003]Generally, in recent motor vehicles, it is demanded of the technical components because of their great number that the volume of the single components and the placement relative to each other be optimized in order to realize the desired function...

AI Technical Summary

Benefits of technology

[0023]Further, the invention relates to developing a refrigerant circuit for the combined refrigeration plant and heat pump operation as well as the afterheating operation for heating, cooling, and dehumidifying the air to be conditioned for the passenger compartment in a constructively simple manner and to provide a process to operate the refrigerant circuit that enables improving the controllability. The unit with the refrigerant circuit is designed to enable the operation with a high refrigeration output at lower heating capacity.

[0066]the possibility of complete circuiting and testing of the HVAC system before mounting it into the vehicle results in fewer quality problems and reworking amount.

Problems solved by technology

Therefore, for example, high-volume components for air conditioning as known from stationary air conditioning units cannot be used because of the limited available space.

Due to the number of the components, different assembly steps are necessary relating to a plurality of connections, which makes the assembly expensive.

In addition, the connections to be made during assembly are potential leakage points that could only be corrected with very much time and cost consumed.

That further increases the installation effort during assembly of the vehicle.

Known systems with coolant-air heat exchangers that receive the heating power from the cooling circuit of an efficient internal combustion engine of the vehicle drive no longer achieve the level demanded for the passenger compartment to be heated up to a comfortable temperature under the conditions of low ambient temperatures such as, for example, −10° C. The same applies for systems in vehicles that are equipped with a hybrid drive.

Consequently, the internal combustion engine will be operated at lower temperatures for a longer time, which negatively affects the exhaust gas emissions and fuel consumption.

Here, waste heat of the internal combustion engine is not available as a potential heat source for heating the air.

It is disadvantageous that, for example, the coolant heater as auxiliary fuel heater delivers its heat power to the engine cooling circuit, which finally transmits the heat over the radiator to the air to be conditioned, hence reaching insufficient dynamics and low efficiency.

The HVAC system is designed for drawing air from the passenger compartment and / or the environment as a compact system placed in a casing, disadvantageously not provided with a heating function.

Disadvantageously, the cooling of the ambient air can lead to ice build-up at the gas cooler, which is operated as evaporator in the heat pump operational mode.

But the usable heating power of the heat pump is reduced.

But also, this operational mode reduces the mean heating capacity of the heat pump.

Heat pump systems where power is transmitted between the refrigerant and air frequently cannot at the same time dehumidify and heat the air supplied to the vehicle.

This results in that the air conditioning unit of a vehicle cannot be operated with recirculated air at low ambient temperatures.

Due to the failing dehumidification function, the remaining humidity of the air and the water delivered by the passengers in form of vapor would lead to fogged window glasses.

For example, for electrically driven vehicles without utilizing motor waste heat, without waste heat of electrical aggregates, or without an additional resistance heating (PTC), there is no possibility to afterheat with low heating power in refrigeration or dehumidifying operational mode of the HVAC system.

Disadvantageously, the HVAC system enables afterheating only in the heat pump operational mode.

The required temperature of the air supplied to the passenger compartment is therefore only providable by increasing the evaporator temperature level, which disadvantageously leads to a lower dehumidification capacity and thus, reduced comfort.

Another important disadvantage of traditional refrigerant circuits of HVAC systems in refrigeration plant operational mode is that the refrigerant on the high pressure side downstream of the gas cooler or condenser cannot be cooled down to a temperature below the ambient temperature.

The heat delivered to cool the refrigerant to high pressure level, however, is transmitted to the low pressure side and re-supplied to the gaseous refrigerant before compression, which reduces the suction density of the refrigerant at the compressor and thus, counteracts the increase in capacity.

In addition, the higher suction temperatures cause higher compression final temperatures, which negatively affect the energy efficiency and service life of the compressor.

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