Density & Conductivity of fluid

Density & Conductivity of fluid Done by: Ng Zi Yao Edmond Chen Kelvin Lim

Definition of fluid A fluid is a substance that continuously undergoes deformation when a force is exerted onto it All gases are fluids, but not all liquids are fluids

Properties of fluids Fluids does not resist deformation, or only resisting it very lightly Fluids has the ability to take the shape of its container

Definition of density Density is defined as an object’s mass per unit volume The S.I. unit for density is kg/m3 It can also be expressed as: ρ = m/V = 1/vg p = density m = mass V = volume Vg = specific volume (volume occupied by a unit of mass)

Instruments to calculate density A common laboratory device is the pycnometer (also known as the specific gravity bottle) It measures the density of a fluid by reference to a common fluid, e.g. water or mercury, using an analytical balance http://www.museumboerhaave.nl/AAcollection/AAJPEGS/M20/11203.jpg

Density of fluid The density of a fluid changes with temperature and pressure Formula when temperature is changed: ρ1 = ρ0 / [1 + β (t1 - t0)] ρ1= final density ρ0 = initial density β=volumetric temperature expansion coefficient t1 = final temperature (Co) t0 = initial temperature

Density of fluid Formula when pressure is changed: ρ1 = ρ0 / (1 - (p1 - p0) / E) p1 = final pressure (N/m2) p0 = initial pressure E = Bulk modulus elasticity (compressibility of a fluid)

Density of fluid The density of water versus temperature and pressure - http://www.engineeringtoolbox.com/fluid-density-temperature-pressure-d_309.html

How density affects efficiency in the heat exchanger In a denser object, the intermolecular distance is shorter Hence, heat energy is able to be transferred from one molecule to another faster Therefore, a denser substance will increase the efficiency of the heat exchanger, while a less dense substance will decrease the efficiency

Conductivity of fluid Watts per metreKelvin British Thermal Unit per hour foot Fahrenheit Defined as the measure of the ability of a material to conduct heat SI Unit: W/(m·K) English Unit: Btu/(hr·ft·°F) Important in designing heat exchangers Heat transfer coefficients in these components are usually computed using correlations which require thermal conductivity data

Formula thickness of conducting surface separating the 2 temperatures quantity of heat thermal conductivity Temperature Gradient temperature difference rate of heat flow total cross sectional area of conducting surface defined as the quantity of heat, ΔQ, transmitted during time Δt through a thickness x, in a direction normal to a surface of area A, due to a temperature difference ΔT, under steady state conditions and when the heat transfer is dependent only on the temperature gradient.

Instruments to Calculate Thermal Conductivity • Hot-wire apparatus can accurately measure and mixtures at temperatures from 30 K to 750 K with pressures to 70 Mpa

Uses of Density • How different materials interact when mixed • To show difference or degree of density in materials

Uses of Density • Density allows you to solve for mass and volume, if given the other quantity. v * rho = m

Crude Oil Case Study

Density Crude Oil 790 - 973 kg/cu.m Water 1000 kg/cu.m

In the event of oil spill, Crude Oil does not mix with sea water (1025.18 kg/cu.m). Oil spill prevents oxygen from reaching marine animals Oil sticks to birds Crude Oil can be easily removed

Bibliography • http://en.wikipedia.org/wiki/Conductivity • http://en.wikipedia.org/wiki/Fluids • http://fluidproperties.nist.gov/thermal.html • http://www.engineeringtoolbox.com/fluid-density-temperature-pressure-d_309.html • http://www.engineeringtoolbox.com/density-specific-weight-gravity-d_290.html • http://en.wikipedia.org/wiki/Density • http://en.wikipedia.org/wiki/Pycnometer • http://images-0.redbubble.com/img/art/border:whitewithdetail/product:laminated-print/size:small/view:preview/363431-4-floating-wood.jpg • http://www.simetric.co.uk/si_liquids.htm

Density & Conductivity of fluid