Air Conditioning Systems: Introduction

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Questions and Answers

What is the main function of an air conditioning plant?

Transferring energy from the conditioned space

Why is a thermal distribution system necessary in an air conditioning system?

To introduce fresh air into the conditioned space

Which factor does NOT influence the selection of an air conditioning system?

Type of refrigerant used

In summer systems, what role does the air conditioning plant play?

Acting as a heat sink Signup and view all the answers

What type of heat has to be supplied to the space in winter?

Sensible and latent heat Signup and view all the answers

Apart from energy transfer, what is another important function of the thermal distribution system?

Maintaining Indoor Air Quality (IAQ) Signup and view all the answers

What is the advantage of variable air volume (VAV) systems over constant volume systems?

Reduced power consumption in perimeter zones Signup and view all the answers

Why can there be problems with ventilation and indoor air quality in very low load situations in variable air volume systems?

The flow rate is too low for proper air distribution Signup and view all the answers

What is a potential difficulty in balancing dampers in variable air volume systems?

Widely varying airflow rates Signup and view all the answers

How do dual duct, constant volume systems provide both cooling and heating to different zones?

By mixing cold and hot air streams in mixing boxes Signup and view all the answers

Why does the dual duct system occupy more space compared to other systems?

Need for larger ducts due to higher airflow rates Signup and view all the answers

What allows dual duct systems to maintain proper indoor air quality and room air distribution?

Total airflow rate variation Signup and view all the answers

In outdoor air control in all air systems, why are the exhaust and outdoor air dampers controlled in unison?

For building pressurization or de-pressurization purposes Signup and view all the answers

How can energy efficiency be improved in dual duct systems during cold weather?

Shutting down the cooling coil Signup and view all the answers

What is the main difference between dual duct, constant volume systems and dual duct, variable air volume systems?

Constant airflow rate to each zone vs. airflow rate reduction based on load Signup and view all the answers

In single duct systems, what is the function of the supply fan?

Control the amount of cooling or heating provided in the coils Signup and view all the answers

What is the primary purpose of a humidistat in single zone air conditioning systems?

Measure humidity ratio and control humidifier Signup and view all the answers

What differentiates dual duct systems from single duct systems in air conditioning?

They use separate supply ducts for hot and cold air Signup and view all the answers

What distinguishes single zone systems from multiple zone systems in air conditioning?

Control based on temperature measured at a single point Signup and view all the answers

What is a characteristic feature of constant volume air conditioning systems?

Maintaining a constant volumetric flow rate of supply air Signup and view all the answers

What happens to return air from the conditioned space in all air systems?

It is conveyed back to the A/C plant for further processing Signup and view all the answers

How does an all water system differ from an all air system in air conditioning classification?

It uses water instead of air as the media for thermal distribution Signup and view all the answers

'Dual duct variable volume systems' are distinguished by their ability to:

Provide variable airflow rates based on demand Signup and view all the answers

What is a defining characteristic of unitary refrigerant-based systems in air conditioning classification?

They rely on refrigerant as the main media for thermal distribution Signup and view all the answers

What differentiates 'constant volume, multiple zone systems' from 'variable volume systems'?

Their adaptability to regulate airflow based on zones' demands Signup and view all the answers

What percentage of supply air flow rate is typically required for ventilation in the described system?

10% Signup and view all the answers

In what temperature range is it recommended to use 100% outdoor air in the air conditioning system?

13°C to 24°C Signup and view all the answers

What is a disadvantage of all air systems mentioned in the text?

Balancing air in large systems could be difficult Signup and view all the answers

What type of buildings may find it difficult to provide air conditioning using all air systems due to space constraints?

High-rise buildings Signup and view all the answers

In all water systems, what happens when cooling is required in the conditioned space?

Cold water is circulated Signup and view all the answers

What type of system is used for either cooling only or heating only application, but cannot be used for simultaneous cooling and heating?

2-pipe system Signup and view all the answers

What does a 2-pipe system in all water systems consist of?

Two pipes Signup and view all the answers

How is the flow rate of hot or cold water to the conditioned space controlled?

By the zone thermostat Signup and view all the answers

Which component is responsible for cooling and dehumidifying the air in a fan coil unit?

Finned tube cooling coil Signup and view all the answers

What is the purpose of a pressure relief valve (PRV) in the water line?

Maintaining balanced flow rate Signup and view all the answers

In a 4-pipe system, how many supply pipelines are there for hot and cold water?

Two each Signup and view all the answers

Which component of the fan coil unit is responsible for drawing warm air from the conditioned space?

Fan Signup and view all the answers

How is heat transfer primarily achieved in a convector?

By natural convection Signup and view all the answers

What can be used to control the capacity of a fan coil unit?

Controlling both air flow rate and water flow rate Signup and view all the answers

What is the main difference between coil control and face-and-bypass control in a single zone system?

The method of controlling zone humidity Signup and view all the answers

In a single duct, single zone system, which space type is suitable for applications of constant volume systems?

Laboratories with precise control requirements Signup and view all the answers

What is a disadvantage of single duct, multiple zone, constant volume systems with reheat coils?

High energy consumption for cooling and reheating Signup and view all the answers

Why might face-and-bypass control be preferred over coil control in a single zone system?

It allows for more precise control of zone humidity Signup and view all the answers

What type of systems are suitable for large buildings with several zones of different cooling/heating requirements?

Single duct, constant volume, multiple zone systems Signup and view all the answers

What is a key advantage of using single duct, multiple zone, constant volume systems with reheat coils?

Ability to control temperature and humidity accurately Signup and view all the answers

What prevents simultaneous cooling and heating in single duct, multiple zone systems with reheat coils?

The inability to switch off any reheat coils Signup and view all the answers

What makes single duct, multiple zone, constant volume systems with reheat coils unsuitable for energy-efficient cooling?

Requirement to first cool and then heat the air Signup and view all the answers

What is a benefit of using face-and-bypass control over coil control in a single zone system?

More precise humidity control Signup and view all the answers

In single duct, variable air volume (VAV) systems, what is the main purpose of the cooling and dehumidifying coil (CC)?

To cool and dehumidify the air to a set level Signup and view all the answers

What is one advantage of air-water systems over all air systems regarding space requirements?

They require less space because the primary airflow is less. Signup and view all the answers

What type of system allows for simultaneous cooling and heating?

Air-water systems Signup and view all the answers

What is the primary air responsible for in an air-water system?

Providing ventilation Signup and view all the answers

What is a disadvantage of air-water systems related to controlling the conditioned spaces?

The primary air cannot be shut down in unoccupied spaces. Signup and view all the answers

Why do unitary refrigerant based systems vary in capacity and type?

To cater to different cooling needs and conditioned spaces. Signup and view all the answers

Which component eliminates the need for a separate ventilation system in an air-water system?

Primary air Signup and view all the answers

What is a common feature of unitary refrigerant based systems?

They consist of separate air conditioning units with individual refrigeration systems. Signup and view all the answers

What type of buildings are most suitable for all water systems using fan coil units?

Office buildings Signup and view all the answers

What is the purpose of the secondary water lines in air-water systems?

Heating the conditioned space Signup and view all the answers

Why are fan coil units used in air-water systems?

To help control both primary air and secondary water. Signup and view all the answers

What can happen if ventilation in an air-water system relies on opening windows?

Dependency on wind and stack effects Signup and view all the answers

In what type of buildings are air-water systems typically used?

Exterior buildings with large sensible loads. Signup and view all the answers

Why is draining condensate water considered messy in air conditioning systems?

It creates health problems if not drained properly Signup and view all the answers

What is a potential issue related to the primary air in air-water systems?

Its supply cannot be shut down in unoccupied areas. Signup and view all the answers

What is a notable advantage of unitary refrigerant based systems?

They are factory assembled and tested as per standard specifications. Signup and view all the answers

Why are fan coil units used in air-water systems for individual zone control?

To control both primary air and secondary water flow rates. Signup and view all the answers

What is a limitation of unitary refrigerant based systems compared to other types of systems?

They are not suitable for perimeter zones only. Signup and view all the answers

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