Transport Phenomena
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1. a. Konduktivitas termal: thermal conductivity, , is the property of a material's ability to conduct heat. It appears primarily in Fourier's Law for heat conduction. Thermal conductivity is measured in watts per kelvin-meter (W·K−1 ·m −1 , i.e. W/(K·m) or in IP units (Btu·hr −1 ·ft −1 ·F −1 , i.e. Btu/(hr·ft⋅F). Dimension of thermal conductivity = M 1 L 1 T −3 K b. Difusifitas termal: thermal conductivity divided by density and specific heat capacity at constant pressure. [1] It measures the ability of a material to conduct thermal energy relative to its ability to store thermal energy. It has the SI unit of m²/s. c. Kapasitas panas: Heat capacity , or thermal capacity , is a measurable physical quantity equal to the ratio of the heat added to (or subtracted from) an object to the resulting temperature change. [1] The SI unit of heat capacity is joule per kelvin and the dimensional form is M 1 L 2 T −2 Θ −1 . d. heat flux: m 2 .s -1 2. K (metals) > K (insulators) > K (liquids) > K (gases) 3. Newton’s law of viscosity and Fourier’s law of heat conduction both are empirical laws, based on the observations. Newton’s law of viscosity describes that momentum flux in any fluid is proportional to the velocity gradients while Fourier’s law describes that heat flux due to conduction is proportional to temperature gradients where velocity and temperature gradients are the driving force, respectively. 4. Sxs 5. Thermal conductivity of metals increases with temperature. For gases, it increases with temperature at low densities while decreases with temperature for most of the liquids. It can be seen that the thermal conductivity of a gas approaches a limiting function of T at low pressures; for most gases this limit is reached at about 1 atm pressure. The thermal conductivities of gases at low density increase with increasing temperature, whereas the thermal conductivities of most liquids decrease with increasing temperature.
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Tugas matakuliah transport phenomena yang merupakan sebagian subbab-subbab yang ada pada bab 2 buku penunjang matakuliah tersebut: Transport Phenomena in Biological system
Transcript of Transport Phenomena
1. a. Konduktivitas termal: thermal conductivity, , is the property of a material's ability to conduct heat. It appears primarily in Fourier's Law for heat conduction. Thermal conductivity is measured in watts per kelvin-meter (WK1 m 1 , i.e. W/(Km) or in IP units (Btuhr1 ft1 F1 , i.e. Btu/(hrftF). Dimension of thermal conductivity = M1 L 1 T 3K
b. Difusifitas termal: thermal conductivitydivided bydensityandspecific heat capacityat constant pressure.[1]It measures the ability of a material to conduct thermal energy relative to its ability to store thermal energy. It has theSIunit of m/s.
c. Kapasitas panas: Heat capacity, orthermal capacity, is ameasurablephysical quantityequal to the ratio of theheatadded to (or subtracted from) an object to the resultingtemperaturechange.[1]TheSIunit of heat capacity isjouleperkelvinand thedimensional formis M1L2T21.
d. heat flux: m2.s-1
2. K (metals) > K (insulators) > K (liquids) > K (gases)
3. Newtons law of viscosity and Fouriers law of heat conduction both are empirical laws, based on the observations. Newtons law of viscosity describes that momentum flux in any fluid is proportional to the velocity gradients while Fouriers law describes that heat flux due to conduction is proportional to temperature gradients where velocity and temperature gradients are the driving force, respectively.
4. Sxs5. Thermal conductivity of metals increases with temperature. For gases, it increases with temperature at low densities while decreases with temperature for most of the liquids.
It can be seen that the thermal conductivity of a gas approaches a limiting function of T at low pressures; for most gases this limit is reached at about 1 atm pressure. The thermal conductivities of gases at low density increase with increasing temperature, whereas the thermal conductivities of most liquids decrease with increasing temperature.
6. For metals (liquids), Prandtl number is very low below 0.1. For non-metal (liquids), it is more than 1 and varies largely. Examples: 13.4 for seawater and 40,000 for engine oil. For gases, it is less than one (0.1 to 0.9).7.
8. In general specific heat(C) gives us an idea of the amount of energy(heat) we need to provide to a system in order to bring about a unit rise in the temperature of the system. It's value may vary depending on the process you are providing this energy. Hence we have two values of C namelyCv andCp .Cvfor a gas is the change in internal energy (U) of a system with respect to change in temperature at a fixed volume of the system i.e.Cv=( U/ T)vwhereas Cpfor a gas is the change in the enthalpy (H) of the system with respect to change in temperature at a fixed pressure of the system i.eCp=( H/ T)p.We know that, H = U + PV (+ VP, P=0 for constant pressure) . So the enthalpy term is greater than the internal energy term because of thePV term i.e in case of a constant pressure process more energy is needed, to be provided to the system as compared to that of a constant volume process to achieve the same temperature rise, as some energy is utilized in the expansion work of the system. And the relation that correlates these twoisCp= Cv+ RBut since liquids and solids can practically assumed to be incompressible, Cpand Cvfor them have almost same values and hence only a single value of specific heat is used for them.The change of entalpy for solid and liquid substances is obtained as a result of a change just in internal energy regardless the change in pressure or volume so Cv = Cp for solid and liquid.. but for gases the enthalpy is a function of temperature and pressure (especially when the change in pressure is higher than few atm.) so the enthalpy is obtained as the change of internal energy plus the effect of volume & pressure changes. for that reason the heat capacity for gases defers when the process is undergoing at P=cost or V=cost .9.
