Energy conversion processes with high environmental impact (by diffusion and / or size) such as refrigeration systems and heat pumps, co-generators and more efficient use of primary energy resources.
Key issues related to energy analysis of buildings and their heating systems.
Course notes. Textbooks are possibly suggested in the notes for the various topics.
All material is available on moodle e-l course https://e-l.unifi.it/course/view.php?id=2558
Learning Objectives
Complete the environmental engineer's energy training with knowledge of high-impact energy conversion (diffusion and / or dimension) processes such as refrigeration and heat pumps, cogenerators and more efficient use of primary energy resources combined gas / steam, recuperative gas turbine cycles, steam generators and cooling towers.
Provide the basic skills needed to approach the energy issues of buildings, in particular for heating, with few notes also to cooling. Acquiring the basic concepts that enable to deal with issues of energy-inefficient buildings (degree day, transmittance, seasonal yields etc.) and the ways to reduce them in a rational and conscious way
Prerequisites
Knowledge of thermodynamics and heat transfer acquired in the energy based courses in the first level degree.
Knowledge of wet air (psychrometry).
Teaching Methods
Lectures, tutorials, seminars and/or educational visits on specific topics
Further information
All information and communications, as well as teaching material, can be found on moodle e-l of the course
https://e-l.unifi.it/course/view.php?id=2558
Type of Assessment
Oral exam: 2-3 questions on course topics, including the resolution of an applicative problem
Course program
1. Refrigeration cycles (about 6 hours) - Performance coefficient (COP). Simple and perfect compression cycles. Absorption cycles. Heat pumps. Refrigerant fluids and environmental compatibility.
2. Powerplants and components for the production of electricity and heat and their impact on the environment: evaluation and possible solutions for the improvement of the energy performance:
a. Cogeneration of electricity and heat (about 4 hours) - Legislative aspects and performance evaluation. Solutions with steam plants, gas turbines and internal combustion engines. Regulatory loads (dynamic analysis).
b. Microcogeneration (about 4 hours): solutions for the production of small distributed electric power and heat (gas microturbines, ORC cycles). Use of low temperature heat (ORC cycles).
c. Steam gas combined cycles (about 3 hours) - Recovery solutions and repowering interventions. Combined cycle performance. Heat recovery Steam Generator (HRSG) efficiency. Heat balance of the HRSG.
d. Steam generators (about 3 hours): air-exhausts and water-steam circuits . Natural circulation, assisted and forced circulation. Corrosion and cleaning of steam generators. Steam generator efficiency: direct and indirect method with calculation of losses.
e. Cooling towers (about 3 hours) - Type, operating principle and preliminary sizing.
3. Heat Transfer Complements (about 5 hours). Conductivity of solids / liquids / gases, temperature dependence. Convection: Principle recall, dimensional numbers. Forced and natural convection. Global heat transfer coefficient. heat exchangers Surface ; efficiency e, NTU thermal exchange unit. Sizing method NTU-e, heat capacity effects.
1) Heat transfer (about 3 hours): basic concepts, heat resistance networks, combined convection + radiation, insulation of walls and windows, insulating materials.
2) Energy performance of buildings (about 12 hours): building casing and heat balance; design conditions for heating and cooling of building rooms; heat loads of buildings; conductive-convective heat transfer through opaque and transparent walls and their losses (vertical walls, roofs, foundations, windows, doors); composite walls; the free contributions of machinery and people; solar gains; calculation of equivalent wall temperature (Tsol-air); shading devices; external infiltrations: air intakes; approach to design and energy consumption of buildings; degree days; calculation of the building's heating requirements; reference to national and European regulations.
3) Building heating Plants (about 10 hours): the average seasonal efficiency of the plants; the series of efficiencies from heat generation to room heat delivery: dependence of individual values on environmental and plant characteristics; choice of generators and calculation of primary energy consumption for heating and domestic hot water production; systems regulation and efficiency; nod to the norms; centralized and autonomous system concept; high-efficiency plants; examples of building energy diagnosis settings. Application of the dynamic analysis of plant - building systems.
4) Unconventional plants and systems (about 6 hours): heat pumps, integration with renewable energies (geothermal, solar thermal, photovoltaic). Possible integration with cogeneration and re-use of low temperature heat from the other part of the course. Fundamentals of dynamic system building analysis - plant (seminar 3 hours).