Final Study Guide Flashcards
m^2 (meters squared)
Area
m^3 (meters cubed)
Volume
m/s (meters per second)
Speed & Velocity
m/s^2 (meters per second squared)
Acceleration
kg/m^3 (kilogram per meters cubed)
Density
m^3/kg (meters cubed per kilogram)
Specific Volume
N (Newtons)
Force
Pa (Pascal)
Pressure
J (Joules)
Energy
W (Watts)
Power
Kelvin, Celsius
Temperature
Pa s (Pascal second)
Dynamic viscosity
kj/kg C (kilojoules per kilogram degrees Celsius)
Specific Heat
kj/kg (kilojoules per kilogram)
Enthalpy
kg (kilogram)
Mass
W / (m k) (Watts per meter kelvin)
Thermal conductivity
J/s (Joules per second)
Watts
Kg x m/s^2 (kilogram times meter per second squared)
Newton
_________ works by moving heat from the cooling area (inside of fridge) to another place where it can be released (heat sink)
- Significant in food preservation
- Lower temperatures slow down reactions that cause food to spoil
- This process uses refrigerants to transfer heat
Refrigeration
Selection of Refrigerants includes:
Example. Ammonia, Freon, Methyl Chloride
- High latent heat of vaporization
- Freezing temperature should be below the evaporator temperature
- Must be non toxic
- Nonflammable
- Not corrosive
- Chemically stable
- Low cost
- Easy leak detection
- No environmental damage
A.S.H.R.A.E stands for_________ and establishes __________
- American Society of Heating, Refrigerating, and Air conditioning Engineers
- Establishes the standards for refrigerants based on safety and chemical properties
Amendment to control substances that lead to stratospheric ozone depletion
Montreal Protocol
4 components of refrigeration system
1) Expansion valve
2) Evaporator
3) Compressor
4) Condenser
The _______ lowers the pressure of the refrigerant, cooling it down before it enters the evaporator
Expansion Valve
The _________ absorbs heat from the cooling area, vaporizing the refrigerant into a gaseous state (latent heat)
Evaporator
Saturated vapor enters the ____________
The _________ compresses the refrigerant gas, increasing its pressure and temperature
Compressor
The _________ releases heat from the refrigerant as it cools and turns back into a liquid, to saturated liquid at the exit
Condenser
True or False: Refrigerant enters the expansion valve as saturated liquid and leaves the evaporator as saturated vapor
True
True or false: The refrigerant is superheated (enters superheated vapor section) before entering the compressor
True
The _________ happens in the evaporator, and is the amount of heat removed from a space or substance to lower its temperature
Hint: Formula is q = m (H2 - H1)
Refrigeration effect
- Each piece of food product is frozen separately
- The process freezes food quickly to preserve quality and texture
- The individual pieces remain separate, making them easy to handle and portion out
- Reduces the risk of freezer burn
IQF (Individually quick frozen)
the loss of moisture from the surface of frozen foods over time during frozen storage causing textural changes and discoloration of food products
Freezer burn
Product and refrigerant are separated by a barrier through out the freezing process
Examples. Plate freezers (barrier by packing material) , Air-blast freezers (circulated air around packaged product)
Indirect contact freezing
- Product and refrigerant have direct contact throughout the freezing system
- No barrier to transfer heat
- Operates more efficiently
Refrigerant: low temperature air, high speed, rapid freezing
Example. Air Blast ( Low air temp in direct contact with small product objects in the form of IQF), Immersion Freezer ( product is immersed in liquid refrigerant, Tunnel freezer, Fluidized bed freezer, non-packaged Spiral freezer
Direct Contact freezing
A commonly used descriptor for the storage life of frozen foods is the _______
Hint: The amount of time a food can be stored in a frozen state while still maintaining its original qualities and staying safe for consumption
PSL. Practical Storage Life
The _________ is the time it took from freezing initial high quality product to the moment when sensory attributes have significantly decreased. The observed difference is termed the __________
High - quality life ; Just Noticeable Difference
A typical microwave oven consists of the following major components:
1) Power supply
2) Magnetron or power tube
3) Wave guide
4) Stirrer
5) Oven cavity
Microwave oven components:
The purpose of the ________ is to draw electrical power from the line and revert it to the high voltage required by the Magnetron
Power supply
Microwave oven components:
The ________ is the core component that converts the power supplied into microwave energy
Magnetron
Microwave oven components:
The _______ propagates, radiates, or transfers the generated energy from the magnetron to the oven cavity
Wave guide
Microwave oven components:
The _______ is usually a fan-shaped distributor that rotates and scatters the transmitted energy throughout the oven.
Stirrer
Microwave oven components:
The ________ encloses the food to be heated within the metallic walls. The energy impinging on the food is absorbed and converted into heat
Oven cavity
Regulatory Agency for Microwaves
A measure of the rate of heat transfer through a composite system
Overall Heat-Transfer Coefficient (OHTC)
Conductive and convective heat transfer occur _______
Simultaneously
- Non-contact
- Indirect heating
- Many layers of tubes (example. Double pipe and triple tube)
- Heating and cooling
Tubular Heat Exchanger
- Indirect heating
- Non-contacting
- Use of plates
- Heating and Cooling
Plate Heat Exchanger
- Direct contact heating
- Applications include: Cooking, Sterilization, Ice cream mixes, Puddings
Steam Infusion heat exchanger
A measure of the density of a substance compared to the density of water
SG (Specific Gravity)
Interpretation of SG:
The substance has the same density as water
SG = 1
Interpretation of SG:
The substance is less than water and will float
SG < 1
Interpretation of SG:
The substance is denser than water and will sink
SG > 1
__________ refers to the total pressure exerted on a system, including both the atmospheric pressure and any additional pressure applied by the system (ex. Vacuum chambers, pressure cookers, sterilizers)
Absolute pressure
A _______ is a device used to measure pressure differences in various processing and storage systems, where precise pressure control is essential for maintaining product quality and safety
Ex. Vacuum packaging
U-tube manometer
3 Modes of heat transfer:
Conduction - heat transfer through direct contact
Convection - heat transfer through fluid movement (liquid or gas)
Radiation - Heat transfer through electromagnetic waves
This instrument measures the amount of total soluble solids in a solution (reading is expressed in degrees Brix to measure sugar content)
Refractometer
- Independent units
- Example. Length, time, temperature, mass
Primary Dimensions
- combination of primary dimensions
- Examples. Volume, Velocity, Area
Secondary dimensions
