99538 - HVAC Systems and Dynamic Energy Simulation M

Academic Year 2024/2025

  • Teaching Mode: Traditional lectures
  • Campus: Bologna
  • Corso: Second cycle degree programme (LM) in Energy Engineering (cod. 5978)

    Also valid for Second cycle degree programme (LM) in Energy Engineering (cod. 5978)

Learning outcomes

At the end of the course, the student possesses the basic knowledge for the design of all-air and mixed conditioning systems as well as for the sizing of mechanical ventilation systems also through the aid of dynamic simulation software. In particular, the student is able to: - Calculate the cooling load and the summer energy requirement of a building; - Sizing the sections of an air handling unit (AHU); - Use dynamic software for the complete modeling of "building-plant" systems.

Course contents

PART 1 (Summer thermal loads and energy requirements)

Summer thermal loads. Calculation of the behavior of a wall in stationary and dynamic conditions.

Thermal transfer matrix of a wall. Physical meaning of the terms of the thermal transfer matrix. Effective heat capacity and dynamic transmittance. Calculation of the attenuation and phase shift of a wall. Role of surface mass and thermal diffusivity on the dynamic characteristics of a wall. Multilayer walls.

Analysis of climatic data (UNI 10349) useful for calculating summer loads. Thermal balance of a room. Energy balance equation for air. Balance equations for individual components. Design and verification problems.

CARRIER method of accumulation factors. Evaluation of sensible heat exchanged by radiation, transmission and ventilation. Solar factor and shading coefficient of a glass element. Concept of accumulation factor for solar radiation and artificial lighting. Equivalent temperature difference. Evaluation of the latent load of the environment.

UNI-TS 11300 standard part 1: calculation of the thermal energy requirement for summer air conditioning of the envelope. Calculation of the transmission dispersion coefficient. Calculation of the extra-flow. Calculation of the component related to the ventilation of the rooms in the case of natural ventilation. Ventilation flow rate according to UNI 10339. Calculation of the component related to the ventilation of the rooms. Calculation of internal loads. Calculation of the solar component. Shading factors. Calculation of the dispersion utilization factor. Calculation of the cooling period.

Summer checks: minimum summer requirements of the envelope. Reference building method. Definition of major renovation of level I and II. Influence of thermal insulation, ventilation, solar absorption coefficient, extra-flow and screens on the summer performance of a building. Screen design.

PART 2 (Air, water and mixed systems)

Air conditioning systems: classification. Main components of an Air Handling Unit (AHU). Types of all-air conditioning systems. Air-vapor mixtures. Balance equations. Adiabatic mixer. Heating batteries. By-pass factor. Cooling battery. Total, latent and sensible power of a battery. Regulation of a cooling battery. Liquid water and vapor humidifier. Definition of R. Evaluation of the input conditions for the conditioning of a room. Architecture of an air conditioning system and summer and winter work cycle.

Elimination of Post-heating in summer. Systems with recirculation and mixed air by-pass: advantages and limitations. Post-heating by means of a heat recovery unit.

Single-duct multi-zone systems: operating principles and work cycles. Different types of multi-zone systems. Double-duct systems with and without cold channel air treatment.

Single and double-duct VAV systems. Water systems. Two-pipe and four-pipe fan coil units. Mixed air-water systems. Induction terminals. Chilled beams. Comparison between mixed systems and all-air systems.

Heat recovery units. Sensible and latent efficiency. Sensible recovery units. Indirect humidification. Sensible and latent recovery units. Dynamic recovery units.

Total and partial direct free cooling. Free cooling with direct humidification (RAD). Free cooling with indirect humidification (RAI). Analysis of work cycles in the presence of only FC, FC+RAD and FC+RAD+RAI. Parameters that influence free cooling. Fields of application.

Sizing of distribution channels. Constant unit pressure drop method. Speed reduction method. Pressure recovery method. Sizing of air distribution systems with fabric ducts. Characteristics of distribution channels. Outlets. Distribution systems: mixing, piston, displacement. Position of outlets and efficiency. Characteristic parameters of inlet outlets.

USING TRNSYS

Introduction to dynamic energy software. What does dynamic simulation mean. The TRNSYS software. Main features and tools. Libraries and types. Building model construction. Building model construction of an air system. Building-system coupling. Simulation results. Data analysis.

Readings/Bibliography

ASHRAE Handbook "Fundamentals" (SI edition)

ASHRAE Handbook "HVAC Systems and Equipment" (SI edition)

Notes by the Teacher

Slides shown in class

Collection of numerical exercises solved

Teaching methods

Each lesson (in Italian) covers both theoretical and practical aspects. At least, one numerical example is shown for each topic.

Lessons are made by using slides (powerpoint).

Assessment methods

The exam is composed by two tests:

1) one written test (a numerical solution of a design problem)

2) one oral test

Teaching tools

Lessons are made by using slides (powerpoint).

A pdf copy of the slides (in Italian) is available for UNIBO students at virtuale.unibo.it.

Office hours

See the website of Gian Luca Morini