In the passenger compartment typically a certain comfort temperature is demanded. In concept phase where only a few data are available, KULI supports the engineer in finding the required evaporator cool load to achieve the design temperature.
The current example represents a very basic configuration of an HVAC system. Air duct, blower and evaporator are simply modeled by heat flow sources, temperature- and mass flow targets with input based on rough assumptions. Using this model, the user can optimize the evaporator air outlet temperature such, that the evaporator cool load will lead to the desired cabin temperature.Usable from release: KULI 8.0-1.04
In the vehicle HVAC system air recirculation mode is used to reach a desired temperature faster and to prevent from bad outdoor smell. On the other hand passenger air quality may suffer from the recirculation. An approach to keep the advantage of recirculation but reduce its disadvantage is the use of mixed air.
The current example is based on “Ex_AC_cool_down_recirc.scs” from the KULI installation setup. Here, the user can set a proportion of fresh and recirculation air that will blow into the cabin.Usable from release: KULI 13.1
On the standard condenser test bench the refrigerant inlet and outlet conditions are fixed and the refrigerant mass flow is the test result. For plausibility checks or for calibration: The corresponding KULI model allows a virtual reproduction of the test bench situation.
The refrigerant condition can be defined by inlet-temperature,-pressure and outlet-subcooling value (à CND-Test_VariantEntryTemp.scs). The air inlet condition is fixed, the air flow can be varied to test for different operating points. The condenser test bench is packed to a subsystem and does not require the user’s attention in first instance. Test results like refrigerant mass flow, heat transfer and pressure loss are collected in another subsystem . Variants of the test bench model require inlet superheat instead of inlet temperature or mean pressure instead of inlet pressure as input (à CND-Test_VariantEntrySH.scs, CND-Test_VariantEntrySH(meanPressure).scs).Usable from release: KULI 14
In the passenger compartment typically a certain comfort temperature is demanded. A possible control strategy to reach comfort level is the use of a PID controller.
The input of the controller is the deviation of the actual temperature to the reference temperature of 22°C. The output value affects e.g. an electro heater with the purpose of minimizing the temperature gap.Usable from release: KULI 8.0-1.04
In real-life cooling packages there will be an non-uniform air flow distribution on heat exchangers, which can have a big effect on heat transfer rate. Using CFD results with KULI it is possible to consider this uneven air flow on heat exchangers.
In the KULI direct CFD interface method *.txt-files containing a velocity distribution from CFD calculation and *.txt-files for writing output like a temperature distribution have to be defined. Unlike the standard/variable resistance matrix method, the direct CFD interface does not require the preprocessing step of calculating a matrix of local resistance corrections. Also unlike the two other methods, here the influence of fans or cp-values on the system air flow are neglected, the system airflow is taken directly from the velocities of the CFD input file. The big benefit of this method is, that KULI can be directly integrated in CFD code, e.g. for iterative underhood computation.Usable from release: KULI 8.0-1.04
This example compares the thermal simulation of a truck cooling system and a simple driving simulation. This proceeding allows the evaluation of the coolant temperatures and the determination of the consumption for a defined driving cycle.
In the past few years hybrid vehicles have been in the center of automotive engineering efforts, in particular in the field of passenger cars. But hybrid powertrains will also be important for commercial trucks. This focus on hybrid vehicles leads to high demands on thermal management since the additional components in a hybrid vehicle need appropriate cooling or even heating.
Beside conventional tasks in energy management, KULI software provides excellent opportunities for the simulation of hybrid- and pure electric vehicles.
This example compares the influence in power consumption of a mid-sized electric car with and without preconditioning (e.g. during a connection with a charger is established).
An extended application of the refrigerant cycle is the use as a heat pump, where the evaporator is used as an auxiliary heater. KULI enables to perform quick analysis of heat pump concepts.
In the corresponding KULI model the real-life evaporator is set up as an KULI condenser-model and vice versa the real-life condenser is set up as an KULI evaporator-model. For investigations in very cold ambient temperatures, where refrigerant low pressure level might fall below ambient pressure an extended media property file of Refrigerant R134a is attached to the example. Sensors and actuators on the inner circuit sheet of KULI allow a good overview on system parameters and results.Usable from release: KULI 8.0-1.04
Especially in HVAC systems using CO2 as refrigerant the evaporator can be used as an auxiliary heater. This can be implemented by switching of the condenser which leads to a triangular process.
In the corresponding KULI model the condenser simply does not exist. For convergence of the calculation model the operation mode “Hot gas cycle mode” has to be activated in the refrigerant circuit definition.Usable from release: KULI 13.1