Block 2 - Gas-Fired Refrigeration Equipment Flashcards
What is sensible heat?
Sensible heat is the thermal energy transferred to or from a substance, resulting in a change in its temperature.
How can sensible heat be measured?
Sensible heat can be measured with a thermometer.
What is latent heat?
Latent heat is the amount of energy absorbed or released by a substance during a phase change without a change in its temperature.
What does latent heat relate to?
Latent heat is associated with the transformation of a substance between solid, liquid, and gaseous states.
Define absorption refrigeration.
Absorption refrigeration is the raising and lowering of temperatures (sensible heat) and changing the state (latent heat) of fluids to create a cooling effect.
What are the components of an absorption system?
An absorption system uses refrigerant, adsorbent, and heat.
What is a key difference between absorption refrigeration and compression refrigeration?
The basic absorption cycle uses no moving parts.
What are the two types of gas-fired absorption systems?
- Ammonia/water
- Lithium bromide/water
Where can ammonia systems commonly be found?
Ammonia systems can be found in an ice arena.
Where are lithium bromide absorption chiller systems typically used?
Lithium bromide absorption chiller systems are typically used in hospitals.
What is the major advantage of the ammonia-water solution?
Water has a strong affinity for ammonia, making them soluble in various operating conditions.
Why is ammonia not used in residential air conditioning applications anymore?
Ammonia is toxic, which limits its applications.
What are the two types of solutions in the ammonia-water system?
- Strong solution: water saturated with ammonia vapor
- Weak solution: water with little to no ammonia
What pressure is typically required for the ammonia system’s boiling point?
The system is typically pressurized to 200–230 Psig (1,400–1,600 kPa).
What is the freezing point of the lithium bromide solution?
-0.26°C
What are the hazards associated with refrigerants?
- Toxicity
- Flammability
- Asphyxiation
- Physical hazards
What are the two main types of hazardous refrigerants?
- Ammonia
- Halocarbons (e.g., Freon®)
What are the health risks associated with ammonia exposure?
- Coughing
- Chest pain
- Breathing difficulty
- Bronchopneumonia
- Pulmonary edema
- Death from bronchial spasm
What is the odor threshold for ammonia?
The odor threshold for ammonia can be as low as 2 ppm.
What personal protective equipment should be used when exposed to ammonia above 50 ppm?
Proper safety equipment must be provided and used.
What can exposure to ammonia cause?
- Severe eye irritation
- Chemical burns
- Permanent blindness
Is ammonia flammable, and what are the explosive limits?
Ammonia is flammable at all concentrations and explosive between 15% and 28% in air.
What are the hazards of lithium bromide?
Lithium bromide can cause mild irritation to skin and eyes and is corrosive to ferrous metals.
What are the safety practices for ammonia use and storage?
- A written health and safety policy
- Written safe work procedures
- Training for supervisors and workers
- Regular worksite inspections
- Incident investigations
What does a WHMIS program ensure?
A WHMIS program ensures workers are instructed in the safe use, storage, handling, and disposal of hazardous materials like ammonia.
What are the three main circuits of an ammonia absorption refrigerator?
Generator, Condenser, Evaporator, Absorber
These components work together to facilitate the refrigeration cycle.
What is the role of the generator in an absorption system?
The generator is the heat energy source that begins and maintains the operating cycle.
What types of energy sources can be used in the generator?
- Steam
- Gas (natural gas or propane)
- Electricity
- Hot water
What happens to the refrigerant in the condenser?
The condenser collects the separated ammonia vapor and removes heat from the vaporized refrigerant, causing it to condense into a liquid.
In the evaporator, what does the liquid refrigerant encounter?
A pressurized hydrogen atmosphere.
What is the function of the absorber?
The absorber attracts and absorbs the refrigerant from the evaporator.
What is lithium bromide classified as?
A salt.
How does the pressure affect the boiling point of water?
If you increase the pressure, water boils at much higher temperatures; if you decrease the pressure, water boils at much lower temperatures.
What occurs when heat is added to a mixture of water and lithium bromide?
The water will evaporate and rise, while the lithium bromide will sink to the bottom.
What are the main components of an absorption chiller?
- Condenser
- Generator
- Evaporator
- Absorber
- Heat exchanger
What is the weak solution line in an absorption chiller?
A mixture of around 50% lithium bromide and 40% water pumped from the absorber through the heat exchanger to the generator.
What happens in the generator section of an absorption chiller?
The lithium bromide and water separate due to a heat source, allowing water to evaporate and rise into the condenser.
What role does the cooling tower play in the condenser?
It passes water through a sealed pipe within the condenser to remove heat from the water vapor, causing it to condense into a liquid.
At what temperature does the water flash and become very cold in the evaporator?
Around 4.5 °C @ 0.84 kPa.
What is the temperature of the chilled water entering the evaporator coil?
Around 12°C (54°F).
What happens to the chilled water after it passes through the evaporator?
It leaves at around 7°C (45°F) and is ready to be pumped around the building to collect more heat.
What occurs to the water vapor produced by the evaporator?
It is attracted and pulled towards the strong lithium bromide solution in the absorber.
What is the effect of the attraction between water particles and lithium bromide in the absorber?
It creates a vacuum in the absorber chamber.
What is the purpose of the cooling tower water loop in the absorber?
It removes heat generated when water and lithium bromide come into contact and condenses residual vapor particles back into a liquid.
Fill in the blank: Water and lithium bromide can be mixed together, but if you add heat then they will _______.
[separate]
What is the purpose of well-documented annual maintenance for industrial direct-fired refrigeration chiller equipment?
Identifying potential issues early, ensuring reliable and efficient operation, reducing the risk of unexpected breakdowns, and extending the equipment’s lifespan.
What should be done prior to commencing any maintenance activities?
Adhere to the manufacturer’s recommended shutdown procedures to ensure safety and prevent damage.
What are safety checks in refrigeration maintenance?
Conducting a thorough safety inspection of the equipment, checking for signs of wear, damage, or deterioration, and verifying that all safety devices are functioning properly.
What is included in the inspection of the combustion system?
Checking the burner assembly for wear, cleaning the burner and combustion chamber, inspecting fuel nozzles, and verifying manifold gas pressure.
What should be inspected on the heat exchanger?
Examine for fouling, scaling, or corrosion and check for refrigerant circuit leaks.
How should the condenser be cleaned?
Using a brush-tipped vacuum or clean, dry compressed air, and applying a condenser cleaning solution for stubborn debris.
What should be inspected in the venting system?
Check for blockages, leaks, corrosion, and verify that vent pipes are clear.
What is the purpose of checking controls and sensors?
To confirm proper operation and calibration of temperature and pressure sensors.
What should be assessed during the inspection of insulation?
Look for damage, wear, or deterioration and repair or replace as necessary.
What is the importance of verifying refrigerant levels?
To maintain system performance and inspect for leaks in the refrigerant circuit.
What should be evaluated regarding electrical components?
Inspect wiring, connectors, and switches for wear or damage and ensure panels are clean.
What should be checked regarding fans and blowers?
Ensure smooth operation, clean blades, and lubricate bearings as recommended.
What is the significance of checking for structural integrity?
To ensure the system is securely mounted and structurally sound for safe operation.
Why is documentation and record keeping important?
To maintain detailed records of maintenance activities, supporting long-term system health.
What is the first step in troubleshooting heat input issues?
Confirming a steady and sufficient supply of the correct fuel.
What should be examined regarding burner operation?
Inspect the burner for proper ignition and stable flame operation.
What should be checked in the control system during troubleshooting?
Look for error codes, faults, and verify the accuracy of sensors.
What should be inspected on heat exchange surfaces?
Check for fouling, scaling, or residue buildup and ensure unobstructed water flow.
What is essential for maintaining adequate ventilation and airflow?
Inspect air intake and exhaust vents for obstructions and confirm proper fan operation.
What safety devices need to be verified?
Pressure relief valves and interlocks to ensure they are functioning properly.
What should be done to troubleshoot venting issues?
Inspect the venting system for visible signs of damage.
What is critical for the proper installation of a venting system?
Compliance with manufacturer specifications and local building codes.
What should be checked for drafting issues?
Test the system to confirm adequate draft and look for negative pressure signs.
What indicates the need for monitoring flue gas temperature?
Abnormally high temperatures may signal incomplete combustion or other issues.
What is important regarding vent termination points?
Ensure proper placement away from air intakes and windows to prevent re-entry of exhaust gases.
What should be done if problems persist during troubleshooting?
Seek assistance from a qualified professional to address underlying issues.
What is a key consideration when inspecting the manufacturer’s specific information?
Understanding the system and checking various parts as per manufacturer’s instructions.
What does the Burner Parts Replacement section display?
The maintenance interval and current operation hours since the last maintenance of the control panel
It is crucial to prevent malfunction of the burner and its related devices from deterioration.
What happens when the required maintenance interval has passed?
The maintenance alarm is activated with the warning ‘Burner parts should be replaced’
Users are advised to contact their local Johnson Controls service center.
What should be checked to prevent electrical system malfunction?
Check the wiring for loose terminals and poor/degraded wire insulation
This helps prevent potential shorts.
What is the purpose of checking the air fuel ratio?
To check if excessive CO is generated by combustion and to measure CO, CO2, O2 for high combustion efficiency
Inspecting the angle and link of fuel control valve and air damper is essential.
What components of the burner should be checked during maintenance?
Burner head, nozzle, cone, etc. that are exposed to high temperature in combustion
Ensuring these parts are in good condition is critical for safety.
What is required for yearly maintenance of refrigeration systems?
Daily repair management and periodic maintenance
This ensures safe operation, high efficiency, and prolonged life of the product.
What are the major inspection items in yearly maintenance?
- Checking of various safety devices and adjustment
- Diagnosis of operation condition and measurement recording
- Management of absorption solution and refrigerant
- Management of combustion unit
- Maintenance of vacuum level
- Diagnosis and repair of pumps
These items help ensure the overall functionality of the system.
What is the benefit of a yearly maintenance contract?
It allows for periodic inspection and repair to maintain the chiller-heater in optimum condition
In case of failure, priority service and parts are provided.
How often is an overhaul of the chiller-heater typically performed?
Every 3 to 5 years
This is apart from periodic maintenance, correction, and repair.
Fill in the blank: The major inspection items include checking the action of various safety devices and _______.
[adjustment]
True or False: The cleaning of heat transfer tubes in the water system is included in the yearly maintenance contract.
False
It is performed by a separate contract.
