Energy Balances
From an energy balance around a heat exchanger, it is clear that the heat duties
calculated on the hot and cold sides should be equivalent. The data obtained
throughout this experiment were consistent with this assertion. This is shown in Figure
4.4. In the figure, it can be seen that the heat duties on the hot and cold sides are
equivalent (within experimental error) for all runs of the finned, double-pipe heat
exchanger. The energy balances for the runs in the other exchangers are similarly
satisfied, as seen in Tables 4.1 and 4.2.
The fact that the energy balances are satisfied allows confidence to be placed in
the data obtained throughout the experiment. This, in turn, allows confidence to be
placed in the scale-up.
Analysis of the Wilson Plots
The Wilson Plot method makes use of the fact that when the velocity of the hot
fluid in a heat exchanger is varied, the only resistance to heat transfer that changes is
the fluid coefficient, h. There are empirical correlations to determine the Nusselt number
as a function of the Reynolds number and the Prandtl number. From these correlations,
it can be shown that h v0.8 for sufficiently high fluid velocity. As such, it follows that a
plot of 1/U versus 1/v0.8 should be linear.
As seen in Figures 4.1, 4.2 and 4.3, the data obtained in this experiment are
consistent with this theory. Plots of 1/U versus 1/v0.8 for all exchangers tested in this
experiment were remarkably linear. This is evident from the coefficient of determination
(R2) values of the best fit lines. The R2 value for the high cold flow rate data in the plate
heat exchanger, for example, was 0.998. This means that 99.8 percent of the variation
in the data is accounted for in the lin...
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...ndations for Future Study
There are a few areas for improvements for future experiments. In future
experiments, the piping system should be better studied so that valves can be set up
more quickly. This would allow for more runs to be accomplished.
In addition, the cold tank should not be filled to capacity in future experiments
because the cold flow rates were not stable when the tank was full. Instead, filling the
tank to about half capacity would produce more stable cold flows, and reduce time until
steady state is reached.
Conclusions
Overall, this experiment successfully examined three different types of heat
exchangers for their feasibility for a scaled up process. Based on the overall heat
transfer coefficients determined experimentally, the plate heat exchanger provides the
most efficient heat transfer and thus should be selected for scale up.
Testing was performed at 23 ºC under the condition of 0% RH at 1 atm with the standard of ASTM D3985. Measurements were taken at three times and the average value was calculated. All specimens were conditioned at ambient conditions.
(Eq. 7) (Eq. 8) are both used to calculate the heat of the solution and the heat of the calorimeter.
values by using buffers set at PH 1, 3, 5, 7, 9. I predict that there
had an absolute error in the slope of only 0.0007 s/°C and the absolute error in the intercept of
When there is a heat exchange between two objects, the object’s temperature will change. The rate at which this change will occur happens according to Newton’s Law of heating and cooling. This law states the rate of temperature change is directly proportional between the two objects. The data in this lab will exhibit that an object will stay in a state of temperature equilibrium, unless the object comes in contact with another object of a different temperature. Newton’s Law of Heat and Cooling can be understood by using this formula:
Volume ratio) than those that make up DEL1 and DEL2, we may be able to reason that diffusion
The porpoise of these is to determine the Specific Heat. Also known as Heat Capacity, the specific heat is the amount of the Heat Per Unit mass required to raise the temperature by one degree Celsius. The relationship between heat and temperature changed is usually expected in the form shown. The relationship does not apply if a phase change is encountered because the heat added or removed during a phase change does not change the temperature.
The graph below shows the heat storage for a latent heat system in the case of a solid-liquid change.
The purpose of the lab was to show the effect of temperature on the rate of
Polman, H., Orobio De Castro, B. & Van Aken, M. A.G. (2008). Experimental Study of the
The process of conduction between a solid surface and a moving liquid or gas is called convection. The motion of the fluid may be natural or forced. If a liquid or gas is heated, its mass per unit volume generally decreases. If the liquid or gas is in a gravitational field, the hotter, lighter fluid rises while the colder, heavier fluid sinks. For example, when water in a pan is heated from below on my stove, the liquid closest to the bottom expands and its density decreases. The hot water as a result rises to the top and some of the cooler fluid descends toward the bottom, thus setting up a circulatory motion. This is also why the heating of a room by a radiator depends less on radiation than on natural convection currents, the hot air rising upward along the wall and cooler air coming back to the radiator from the side of the bottom. Because of the tendencies of hot air to rise and of cool air to sink, radiators are positioned near the floor and air-conditioning outlets near the ceiling for maximum efficiency.
...inty between 1.0% (0.1/10.00*100) and 2.13% in the measured volume and 0.1/4.70*100). We also used a digital thermometer that allowed us to read the temperature readings from five degrees celcius to eighty degrees celcius. Since the digital thermometer have an absolute accuracy of plus or minus one degree celcius, it gives a percent uncertainty between 0.125 % (0.1 / 5.00 * 100) and 0.2 % (0.1/ 80.0 * 100). One of the difficulties we faced during the lab is reading the inverted graduated cylinder. To account for the inverse meniscus, we subtracted 0.2 mL from all the volumetric measurements to account for that. Volumetric uncertainty is the most important in determining the accuracy of this experiment since we are constantly checking for the volume throughout the lab. It also is the factor that gives the highest percent uncertainty out of all the instruments used.
Heat Transfer describes the process of heat energy being transported when a system moves from one equilibrium state to another. Heat Transfer is divided into three modes: Conduction, Convection, and Radiation
found the results of this test to be fascinating as these results without a fault explained the