Mass and Energy Balances In this chapter we will apply the conservation of mass and conservation of energy laws to open systems or control volumes of interest The balances will be applied to steady and unsteady system such as tanks, turbines, pumps, and compressors 4 1 Conservation of Mass The general balance equation can be written as
• Energy balance – For any system, the energy going into the system must equal the energy coming out of the system plus any accumulation of energy in the system • Only ONE energy balance equation is written for any system (or sub-system) irrespective of the number of components in the product(s) Note: Once mass and energy balance
This makes mass balances more complicated Need to review/introduce some ideas about reactions Stoichiometry Represents molar participation in a reaction How do you do it? Like a mini mass balance (Can only balance atomic species NOT total moles or moles (mass) of compounds) Left hand side is inlet, right hand side is outlet SO2 +02->SO3
Energy Balance Energy Tracker Instructions: Track your energy balance Fill in the foods you eat and their caloric values, as well as your exercises and their calorie-burning power Answer the questions about your energy balance DAY 1 Food Time Eaten Calories Exercise Time Began Duration Calories Burned Breakfast Lunch Dinner Snacks
Overall mass balance: 10 + m 12 = 4 + m Starch balance: 0 2 (10) = 4 (x 12) + 0 4 (m ) Vitamin balance (1): x 2 = 0 Vitamin balance (2): x 3 = 0 Energy balance: 10 {c p(1)}(283 - 273) + m 1 H s = 4{c p(2)}(293 - 273) + m 2 {c p(3)}(T - 273) Second sub-system Overall mass balance: m 24 + 6 = m Starch balance: 0 4 (m 27) = 16 (x ) Vitamin balance
In this chapter we will apply the conservation of mass and conservation of energy If there is no chemical reaction, the mass balance equation is simplified to cv
process flow, Material and energy balance diagrams Material quantities, as they pass through processing operations, can be described by material balances
Water mass flow rate evaporated e) Heat dissipation Se desea enfriar una Mass and energy balance equations for the tower: mass balance for dry air: x x m