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DESIGN AND DEVELOPMENT
OF AUTOMOTIVE HVAC SYSTEMS
GOAL OF COURSE: Provide the basic fundamentals for a systematic approach in the design
and development of an automotive, agricultural, military, off highway equipment HVAC systems that meet all customer expectations
and comfort.
OBJECTIVE: The objective of the intensive two day HVAC seminar is to study the different components
of the Automotive HVAC system and to demonstrate how they may be combined to produce an effective, pleasing to the customer
product. Emphasis is placed on safety, quality, timing and cost. The contribution of the HVAC system on emissions and fuel
economy is also presented. The importance of communication and interaction with different engineering groups and disciplines
are stressed to enable the most efficient packaging of the HVAC system within the real estate constraints of the vehicle.
AUDIENCE: Although the seminar is directed to HVAC designers, technicians and engineers, its purpose is to also inform
and familiarize HVAC basic concepts to those areas which are involved with HVAC. These would include program management, design
studio, packaging, materials, manufacturing, CFD, engine cooling, aerodynamics, thermodynamics, engine control and scientific
laboratory groups.
PHILOSOPHY OF DESIGN: The customer's comfort from both physiological and safety view points
is the basis of design. The power requirements of the HVAC system and its impact on emissions and fuel economy, warranty,
cost and packaging are also a part of the design basis.
DESIGN PROCEDURE: The presentation is divided into four
parts, i.e., Hardware, Fundamentals, Design and Development. The students are first introduced to the various components,
their function and their location in the HVAC system. Fundamental heat transfer equations and HVAC thermodynamic principles
are then discussed. A detailed model design roadmap is then specified and the evaporator, compressor and condenser are sized.
The front end (condenser) and cabin (evaporator) air flow needs are established and the required air moving and distribution
components are selected. A comparison of the theoretical and actual compressor horsepower is made.
The heater is
discussed as a distinct part of the HVAC system including its performance dependence on coolant flow (engine pump) and coolant
heat quantity (spark strategy). Properties of the coolant and corrosion are presented. The routing of the heater and AC lines
and connections are a part of this design model.
The advantages and disadvantages of different flow devices, i.e.,
fixed orifice tube, variable orifice valve, thermal expansion valve and constant pressure valve are discussed. The methodology
of sizing the flow devices based on the refrigerant requirements is presented. The importance of properly sized and routed
AC plumbing and connections is included as part of the flow device design.
The HVAC control system function and
its major components, both ATC and manual, are investigated. The importance of the control system relative to customer satisfaction
and protection of the AC and heater components is stressed.
DEVELOPMENT PROCEDURE: the students are introduced
to the different development tests required to finalize the HVAC design. The importance of first doing an analytical analysis
of the expected results and then confirming the results in an environmental chamber, wind tunnel or in the field is emphasized.
The comparison of actual perfromance to ideal performance is stressed.
The test procedures discussed include:
a. in vehicle air, refrigerant and coolant flow non-uniformity and correction of the supplier's performance curves.
b. determination of the front end and cabin air flow phenomena.
c. sizing of the body exhausters.
d. methodology for determining refrigerant quality and isentropic efficiency.
e. condensate balance, water carry
over and odor prevention.
f. standard soak, cool down, warm up and defrost tests.
g. sizing the orifice
tube and thermal expansion device.
h. refrigerant and compressor oil charge and OCR (oil circulation rate) determination.
i. determining optimum refrigerant condenser subcooling and evaporator superheat.
j. juries and field testing
procedures.
ASSOCIATED AREAS: The use of alternative refrigerants, including carbon dioxide, the anticipated Revised
Federal Test Procedure and its affect on emissions and eventually on fuel economy, component and system warranty and durablity,
the setting of functional objectives, OEM and Supplier relations and a general approach on how to most effectively accomplish
the goals of designing and developing a world class HVAC system while still meeting cost and timing constraints are all an
integral part of the design and development presentation.
INSTRUCTOR'S EVALUATION: An evaluation of the seminar
is provided to the seminar requestor as part of a Summary Report submitted at the conclusion of the seminar
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