Engineers that design or develop systems for the production or processing of biological materials need a basic understanding the thermodynamic concepts pertinent to processing of biological products. This chapter contains a review of the basic concepts and lays a foundation for the subsequent chapters. The student is expected to be able to conduct a mass and energy balance on a biological system.
Thermodynamics is the study of the dynamics of energy exchange between components within a system and the system's surroundings. A boundary is used to enclose the components of a system. System boundaries are used to isolate a system by forming a control volume or control surface. The intrinsic and extrinsic properties of the system define its state. Extrinsic properties such as volume, mass, and energy change with the mass of the system. Intrinsic properties are those that are the same for part or all of the system. Temperature, pressure and density are examples of intrinsic properties.
NOMENCLATURE
| Symbol | Description | SI Units | English Units | |
| Mdb | Moisture content, dry basis | decimal or % |
decimal or % |
|
| Mwb | Moisture content, wet basis | decimal or % |
decimal or % |
|
| mH2O | Mass of moisture | kg |
lb |
|
| Mdm | Mass of dry matter | kg |
lb |
|
| rh | Relative humidity | decimal |
Decimal |
|
| T | Absolute temperature | K |
R |
|
| Me | Dry-basis equiriblium moisture content | % |
% |
|
| c, e | Constants based on material | |||
| P | Pressure | Pa |
psi |
|
| P0 | Pressure exerted on the upper surface of the column | Pa |
psi |
|
| r | Density of fluid | kg/m3 |
lbm/ft3 |
|
| g | Gravity | m/s2 |
ft/s2 |
|
| h | Vertical column of fluid | m |
Ft |
|
| Ph | Pressure head/column height of fluid | Pa |
psi |
|
| Pabsolute | Absolute pressure | Pa |
psi |
|
| Pgauge | Gauge pressure | Pa |
psi |
|
| Patomosphere | Atmospheric pressure | Pa |
psi |
|
| V | Volume | m3 |
ft3 |
|
| n | Number of moles | mole |
mole |
|
| R(bar) | Universal gas constant | 8.314 N m/mol K |
1545 ft lbf/lbm-mole R | |
| R | Specific gas constant (for a particular gas) | N m/mol K |
ft lbf/lbm-mole R |
|
| mf | Liquid fraction | kg |
lb |
|
| mv | Vapor fraction | kg |
lb |
|
| Vf | Volum of liquid | m3 |
ft3 |
|
| Vg | Volum of vapor | m3 |
ft3 |
|
| x | Mass ratio vapor to total mass | |||
| vfg | Difference between vapor and liquid volume | m3 |
ft3 |
|
| H | Total enthalpy | kJ |
ft lbf |
|
| h | Specific enthalpy | kJ/kg |
ft lbf/lbm |
|
| u | Internal energy | kJ/kg |
ft lbf/lbm |
|
| v | Specific volume | kJ/kg |
ft lbf/lbm |
|
| pA | Partial pressure of component A | |||
| xA | Mole fraction of component A | |||
| P° | Vapor pressure of a pure liquid | Pa |
psi |
|
| p | Vapor pressure of water as a temperature T | Pa |
psi |
|
| Po | Saturation vapor pressure of water as a temperature T | Pa |
psi |
|
| E | Total Energy | kJ |
Btu |
|
| KE | Kinetic Energy | kJ |
Btu |
|
| PE | Potential Energy | kJ |
Btu |
|
| U | Total Internal Energy | kJ |
Btu |
|
| A | Cross sectional area | m2 |
Ft2 |
|