Podcast
Questions and Answers
Which factor does NOT affect the boiling liquid side surface coefficient?
Which factor does NOT affect the boiling liquid side surface coefficient?
- Cleanness of the heating surface
- Viscosity of fluid
- Heat content of condensate (correct)
- Velocity of flow of milk
In the heat balance equation, what does the term 'F.hF' represent?
In the heat balance equation, what does the term 'F.hF' represent?
- Heat content of concentrate
- Enthalpy of steam
- Heat content of vapor
- Heat content of feed (correct)
According to the material balance, which equation accurately represents the relationship among feed, output rate of concentrate, and rate of vapour production?
According to the material balance, which equation accurately represents the relationship among feed, output rate of concentrate, and rate of vapour production?
- F = L + V (correct)
- F = L - V
- L = F + V
- V = L - F
When applying the balance equations, if the solids in vapour are taken as zero, what simplification occurs?
When applying the balance equations, if the solids in vapour are taken as zero, what simplification occurs?
What is the relationship between the feed rate and the rate of vapour production based on the provided equations?
What is the relationship between the feed rate and the rate of vapour production based on the provided equations?
Which process is described as a faster method of producing vapors?
Which process is described as a faster method of producing vapors?
What mainly influences the rate of evaporation?
What mainly influences the rate of evaporation?
Under what condition does evaporation typically occur?
Under what condition does evaporation typically occur?
How is vapourization visually detected?
How is vapourization visually detected?
What condition controls the process of vapourization?
What condition controls the process of vapourization?
When will evaporation cease in a closed system?
When will evaporation cease in a closed system?
Which factor has the least effect on the escape rate of surface molecules during evaporation?
Which factor has the least effect on the escape rate of surface molecules during evaporation?
What enhances the removal of water from a liquid product by evaporation?
What enhances the removal of water from a liquid product by evaporation?
What is a main characteristic of falling film evaporators compared to rising film evaporators?
What is a main characteristic of falling film evaporators compared to rising film evaporators?
Which of the following characteristics is true for rising film evaporators?
Which of the following characteristics is true for rising film evaporators?
Which material is primarily used for constructing evaporator bodies and tubes due to its corrosion resistance?
Which material is primarily used for constructing evaporator bodies and tubes due to its corrosion resistance?
What is a typical design consideration for evaporators operating under vacuum?
What is a typical design consideration for evaporators operating under vacuum?
How does the presence of static head affect rising film evaporators?
How does the presence of static head affect rising film evaporators?
Which of the following statements about falling film evaporators is correct?
Which of the following statements about falling film evaporators is correct?
What type of head is typically designed for the bottom of the evaporator drums?
What type of head is typically designed for the bottom of the evaporator drums?
What is a common issue faced by rising film evaporators compared to falling film evaporators?
What is a common issue faced by rising film evaporators compared to falling film evaporators?
What is a characteristic of a dry condenser?
What is a characteristic of a dry condenser?
How much cooling water is needed for a jet condenser compared to the weight of vapor?
How much cooling water is needed for a jet condenser compared to the weight of vapor?
What is a notable advantage of a counter flow type condenser?
What is a notable advantage of a counter flow type condenser?
What causes an increase in the quantity of air removed from the evaporator system?
What causes an increase in the quantity of air removed from the evaporator system?
What type of condenser maintains vacuum while allowing condensate to escape?
What type of condenser maintains vacuum while allowing condensate to escape?
What pressure corresponds to a hydrostatic head of 10.35 meters of water?
What pressure corresponds to a hydrostatic head of 10.35 meters of water?
What is the specific volume of vapor at a boiling point of 60 oC?
What is the specific volume of vapor at a boiling point of 60 oC?
Which type of condenser is preferred for milk evaporating operations due to its cost-effectiveness?
Which type of condenser is preferred for milk evaporating operations due to its cost-effectiveness?
What is the effect of increasing the number of effects in a multiple-effect evaporator on heat flux per effect?
What is the effect of increasing the number of effects in a multiple-effect evaporator on heat flux per effect?
What is the primary concern when evaluating the cost-effectiveness of multiple-effect evaporation systems?
What is the primary concern when evaluating the cost-effectiveness of multiple-effect evaporation systems?
When can the evaporation capacity of a system be significantly reduced?
When can the evaporation capacity of a system be significantly reduced?
Which calculation is NOT typically required for a multiple-effect evaporator system?
Which calculation is NOT typically required for a multiple-effect evaporator system?
What method is indicated as convenient for solving equations related to multiple-effect evaporators?
What method is indicated as convenient for solving equations related to multiple-effect evaporators?
What is the correct first step in calculating for triple-effect evaporators?
What is the correct first step in calculating for triple-effect evaporators?
What primarily affects the values needed for calculations in a multiple-effect evaporator?
What primarily affects the values needed for calculations in a multiple-effect evaporator?
What happens when evaporation processes exceed five or seven effects in terms of economy?
What happens when evaporation processes exceed five or seven effects in terms of economy?
Study Notes
Evaporation & Vapourization
- Evaporation and vapourization occur when molecules gain enough energy to escape from a solution as vapour.
- The rate of escape depends on temperature, pressure, surrounding temperature, surface area and heat propagation rate.
- Evaporation continues in a closed container until the air is saturated with molecules.
- Removal of water from a liquid is enhanced by adding heat and removing saturated air.
Evaporation Types
- Vapourization: A faster process that depends on the pressure above the liquid, the amount of solute and the boiling point being reached.
- Evaporation: A relativity slow process dependent on temperature differences and vapour pressure differences between air and liquid.
- Vapourization produces visual bubbles rising from the surface.
- Evaporation usually isn't visually detectable.
Falling Film vs Rising Film Evaporators
- Rising Film: Has longer residence time and requires more temperature difference. Less overall heat transfer coefficient.
- Falling Film: Shorter residence time and requires less temperature difference. Overall heat transfer coefficient is higher. It's used for heat sensitive products, with less fouling.
Evaporator Design
- Evaporator bodies and tubes are usually made of stainless steel to prevent corrosion.
- Evaporator Drums operate under vacuum conditions.
- Calandria is designed as a tube heat exchanger and based on steam pressure.
- Conical head, calandria and vapour drum are connected by flanged joints.
- Large openings must be reinforced with compensating rings.
Heat & Material Balance
- Heat Balance Equation: F.hf + S.Hs = L.hL+ V.H + Shc (neglecting heat losses)
- Material Balance Equation: F= L+V
- Solid Material Balance Equation: FxF = LxL + Vy
- Capacity Equation based on Solid Material Balance: V = F[ 1- (xf/ xL)]
Condensers
- Dry Condensers use two pumps, one for cooling water and one for non-condensable gases.
- Wet Condensers: remove condensate and non-condensables together.
- Jet Condensers: mix the water and vapour, often used in milk evaporation.
- Counter-Flow Condenser: Requires less cooling water.
- Air Removal: Air removal from the evaporator system is essential for efficient operation.
Barometric Leg Condenser
- It's designed to remove water and condensate without losing vacuum.
- The liquid in the leg creates a hydrostatic head that balances the vacuum.
Multiple-Effect Evaporators
- Increases steam economy but reduces heat flux per effect.
- The complexity of the equipment leads to increased heat losses and decreased capacity.
- Boiling-point rise reduces the capacity of the system.
Multiple-Effect Evaporator Calculations
- Determining the area of the heating surface, the steam supply rate and the amount of vapour leaving each effect are the main calculations.
- Calculation methods are based on material and heat balances, and heat transfer equations.
Triple-Effect Evaporator Calculations
- Step 1: Determine the boiling point in the last effect.
- Step 2: Determine the total amount of vapor evaporated by material balance.
- Step 3: Estimate temperature drops in each effect and calculate the boiling point within each effect.
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Description
Test your knowledge on evaporation and vapourization processes. This quiz covers the principles of how molecules escape from solutions, the factors affecting the rate of evaporation, and the differences between vapourization and evaporation. Additionally, it explores various types of evaporators.
