Week 1 Lecture Note f473x
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Week 1 Lecture Note: MEC740 ENVIRONMENTAL CONTROL IN BUILDINGS
1/4
Introduction What can you deduce from the title of this course “environmental control in buildings”? We want to artificially create and maintain an indoor environment to specific criteria by means of using a heating, ventilating, air-conditioning and refrigeration (HVAC&R) system. The primary function of a HVAC system is to maintain environment conditions in a space that are: 1. conducive to human comfort, and 2. required by a product or a process within a space. In simple , the environmental conditions can be described by 1. temperature 2. humidity 3. air cleanliness and quality 4. air motion 5. noise Environmental conditions in a space are affected by parameters such as: 1. Local atmospheric conditions (referred to as outdoor) (e.g. temperature, relative humidity, wind speed and direction, precipitation, sun, etc.) 2. Physical characteristics of the building (e.g. high rise, materials, glazing, heat sources) 3. Ventilation requirements (e.g. contaminant generation) To maintain the environmental conditions in a space within acceptable limits, HVAC equipment and systems are installed, which provide: (see handout “Basic Terminology”) • heating • cooling • humidification • dehumidification • ventilation (fresh air) • cleaning If the HVAC equipment is sized to provide the acceptable conditions under worst case conditions, i.e. design load, below which, the equipment operates at part load. Therefore, automatic controls are necessary to modulate the operation of the equipment. The objective of this course is to develop proficiency in the following subjects: 1. learn about the HVAC systems, their characteristics, operation principles, selection and design 2. learn about HVAC system components 3. learn how to select indoor/outdoor design conditions 4. learn how to determine heating/cooling, associated humidification/dehumidification loads, and ventilation requirements 5. learn about control of HVAC systems 6. learn about estimation of energy requirements of HVAC systems 7. use of computer software for load estimation and design
Week 1 Lecture Note: MEC740 ENVIRONMENTAL CONTROL IN BUILDINGS
2/4
Air-Conditioning Systems (Chapter 2) Air-conditioning system ⇒ All of the equipment necessary to provide HVAC in a building or its parts Selecting a system: 1. Provide the required performance 2. Fit in the available space 3. Give the owner the best combination of capital or 1st cost, operation cost, and reliability The selection process of an air-conditioning system involves an exhaustive and quantitative analysis, which may includes preliminary design, energy simulation analysis, and cost estimation. An air-conditioning system can be a central system (more than one zone served) or a unitary (packaged) system (usually one zone). zone (definition): is a part of a building which is thermally independent (unique) from other such parts, thus required its own thermostat and/or humidistat. Space air conditioning requirements to be considered for system selection: 1. spaces with uniform loads 2. buildings with large interior cores 1 4
5
2
e.g. A building with 5 zones: Zone #5 is a large interior core, which may have a thermostat range (dead band), e.g., 71 to 73ºF in order to maintain an average of 72ºF.
3 3. spaces requiring precision control 4. large building An air-conditioning system is comprised of (see Fig. 2-1 on pg. 23): 1. primary systems: to convert energy in a fuel to thermal energy for cooling and heating 2. secondary systems (air handler): to distribute heating and cooling as well as fresh (outdoor) air to spaces Primary systems Primary system components: 1. Heating equipment: Boilers – Steam, Hot water Classification: 1. By working pressure/temperature: Low pressure: maximum working pressure of 15 psig for steam, 160 psig for hot water, with a maximum temperature of 250ºF. Medium to high pressure: > 15 psig for steam > 160 psig for hot water 2. Materials of construction:
Week 1 Lecture Note: MEC740 ENVIRONMENTAL CONTROL IN BUILDINGS
3. 4. 5. 6.
3/4
a) Cast iron (sectional) b) Steel (tubes – water tube or fire tube) Fuel used (oil, natural gas, coal, electricity, or waste material) Construction (sectional, round, fire tube) Type of combustion air handling system (natural draft, forced draft, induced draft) By type of application (space heating, domestic hot water (DHW) heating, or both)
Boiler HP = 33475 Btu/hr = 9.81 kW
(usually used to size boiler)
Warm air furnaces High boy:
Furnace
Low boy:
Horizontal:
Furnace Blower
Blower
Blower Furnace
2. Refrigeration equipment or chiller: 1 ton of refrigeration = 12000 Btu/hr = 3.52 kW 1) Vapour compression ⇒ requires shaft work • Reciprocating (1/16 to 150 hp or 50 W to 112 kW) (see Fig. 15-5 on pg. 541) • Orbital scroll (1 to 15 tons or 3.5 to 5.3 kW) (see Fig. 15-11 on pg. 547) • Helical rotary (100 to 1000 tons or 350 to 3500 kW) (see Fig. 15-10 on pg. 546) • Centrifugal (100 tons or 350 kW to higher capacity depending of size) (or turbo compressor) 2) Absorption refrigeration ⇒ requires heat (available in large units from 50 to 1500 tons or 176 kW to 5 MW) Chillers (which are either operating in the vapour compression, absorption or air cooled) – for cooling water or other fluid that is circulated in the cooling system Direct expansion (D-X) coil – a direct heat exchange between the refrigeration in evaporator coil and the supply air Cooling tower is used to remove the heat from the water-cooled condensers of air-conditioning system by ing the water with the atmosphere.
Week 1 Lecture Note: MEC740 ENVIRONMENTAL CONTROL IN BUILDINGS
3. Pumps: • • • 4. Piping:
4/4
to pump chilled water, hot water, condenser water, steam condensate return, boiler feed water, fuel oil in-line pumps (are ed by piping) (small centrifugal pump, quiet, and up to 1 hp and 1750 rpm) close-coupled pumps (impeller on the same shaft as the motor) (1/4 to 40 hp, and 1750 to 3450 rpm) based-mounted pumps (motor is connected to the impeller shaft by a flexible coupling, speed can be changed by pulleys and belt drives (1/4 hp and up, 1750 to 3450 rpm) • •
in the main equipment room – fuel lines, refrigerant piping, steam, water connections in the air-handling systems – hot water supply and return, chilled water supply and return, steam supply line, condensate drainage
1/4
Introduction What can you deduce from the title of this course “environmental control in buildings”? We want to artificially create and maintain an indoor environment to specific criteria by means of using a heating, ventilating, air-conditioning and refrigeration (HVAC&R) system. The primary function of a HVAC system is to maintain environment conditions in a space that are: 1. conducive to human comfort, and 2. required by a product or a process within a space. In simple , the environmental conditions can be described by 1. temperature 2. humidity 3. air cleanliness and quality 4. air motion 5. noise Environmental conditions in a space are affected by parameters such as: 1. Local atmospheric conditions (referred to as outdoor) (e.g. temperature, relative humidity, wind speed and direction, precipitation, sun, etc.) 2. Physical characteristics of the building (e.g. high rise, materials, glazing, heat sources) 3. Ventilation requirements (e.g. contaminant generation) To maintain the environmental conditions in a space within acceptable limits, HVAC equipment and systems are installed, which provide: (see handout “Basic Terminology”) • heating • cooling • humidification • dehumidification • ventilation (fresh air) • cleaning If the HVAC equipment is sized to provide the acceptable conditions under worst case conditions, i.e. design load, below which, the equipment operates at part load. Therefore, automatic controls are necessary to modulate the operation of the equipment. The objective of this course is to develop proficiency in the following subjects: 1. learn about the HVAC systems, their characteristics, operation principles, selection and design 2. learn about HVAC system components 3. learn how to select indoor/outdoor design conditions 4. learn how to determine heating/cooling, associated humidification/dehumidification loads, and ventilation requirements 5. learn about control of HVAC systems 6. learn about estimation of energy requirements of HVAC systems 7. use of computer software for load estimation and design
Week 1 Lecture Note: MEC740 ENVIRONMENTAL CONTROL IN BUILDINGS
2/4
Air-Conditioning Systems (Chapter 2) Air-conditioning system ⇒ All of the equipment necessary to provide HVAC in a building or its parts Selecting a system: 1. Provide the required performance 2. Fit in the available space 3. Give the owner the best combination of capital or 1st cost, operation cost, and reliability The selection process of an air-conditioning system involves an exhaustive and quantitative analysis, which may includes preliminary design, energy simulation analysis, and cost estimation. An air-conditioning system can be a central system (more than one zone served) or a unitary (packaged) system (usually one zone). zone (definition): is a part of a building which is thermally independent (unique) from other such parts, thus required its own thermostat and/or humidistat. Space air conditioning requirements to be considered for system selection: 1. spaces with uniform loads 2. buildings with large interior cores 1 4
5
2
e.g. A building with 5 zones: Zone #5 is a large interior core, which may have a thermostat range (dead band), e.g., 71 to 73ºF in order to maintain an average of 72ºF.
3 3. spaces requiring precision control 4. large building An air-conditioning system is comprised of (see Fig. 2-1 on pg. 23): 1. primary systems: to convert energy in a fuel to thermal energy for cooling and heating 2. secondary systems (air handler): to distribute heating and cooling as well as fresh (outdoor) air to spaces Primary systems Primary system components: 1. Heating equipment: Boilers – Steam, Hot water Classification: 1. By working pressure/temperature: Low pressure: maximum working pressure of 15 psig for steam, 160 psig for hot water, with a maximum temperature of 250ºF. Medium to high pressure: > 15 psig for steam > 160 psig for hot water 2. Materials of construction:
Week 1 Lecture Note: MEC740 ENVIRONMENTAL CONTROL IN BUILDINGS
3. 4. 5. 6.
3/4
a) Cast iron (sectional) b) Steel (tubes – water tube or fire tube) Fuel used (oil, natural gas, coal, electricity, or waste material) Construction (sectional, round, fire tube) Type of combustion air handling system (natural draft, forced draft, induced draft) By type of application (space heating, domestic hot water (DHW) heating, or both)
Boiler HP = 33475 Btu/hr = 9.81 kW
(usually used to size boiler)
Warm air furnaces High boy:
Furnace
Low boy:
Horizontal:
Furnace Blower
Blower
Blower Furnace
2. Refrigeration equipment or chiller: 1 ton of refrigeration = 12000 Btu/hr = 3.52 kW 1) Vapour compression ⇒ requires shaft work • Reciprocating (1/16 to 150 hp or 50 W to 112 kW) (see Fig. 15-5 on pg. 541) • Orbital scroll (1 to 15 tons or 3.5 to 5.3 kW) (see Fig. 15-11 on pg. 547) • Helical rotary (100 to 1000 tons or 350 to 3500 kW) (see Fig. 15-10 on pg. 546) • Centrifugal (100 tons or 350 kW to higher capacity depending of size) (or turbo compressor) 2) Absorption refrigeration ⇒ requires heat (available in large units from 50 to 1500 tons or 176 kW to 5 MW) Chillers (which are either operating in the vapour compression, absorption or air cooled) – for cooling water or other fluid that is circulated in the cooling system Direct expansion (D-X) coil – a direct heat exchange between the refrigeration in evaporator coil and the supply air Cooling tower is used to remove the heat from the water-cooled condensers of air-conditioning system by ing the water with the atmosphere.
Week 1 Lecture Note: MEC740 ENVIRONMENTAL CONTROL IN BUILDINGS
3. Pumps: • • • 4. Piping:
4/4
to pump chilled water, hot water, condenser water, steam condensate return, boiler feed water, fuel oil in-line pumps (are ed by piping) (small centrifugal pump, quiet, and up to 1 hp and 1750 rpm) close-coupled pumps (impeller on the same shaft as the motor) (1/4 to 40 hp, and 1750 to 3450 rpm) based-mounted pumps (motor is connected to the impeller shaft by a flexible coupling, speed can be changed by pulleys and belt drives (1/4 hp and up, 1750 to 3450 rpm) • •
in the main equipment room – fuel lines, refrigerant piping, steam, water connections in the air-handling systems – hot water supply and return, chilled water supply and return, steam supply line, condensate drainage
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