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.
Furthermore, using a graduated cylinder with markings below the 100 mL line would have allowed for more accurate measurements of the initial volume of air in the graduated cylinder.
The results of this experiment are shown in the compiled student data in Table 1 below.
I removed the hand that was covering the hole of the tube when it was under the water of the bowl. The water remains inside the cylinder. all the way to the top, this will allow us to see how much gas is. given by the amount of water forced out of the tube. The delivery tube was then placed inside of measuring cylinder to.
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:
good emitter of heat radiation so a lot of heat will be lost to the
Specific heat capacity of aqueous solution (taken as water = 4.18 J.g-1.K-1). T = Temperature change (oK). We can thus determine the enthalpy changes of reaction 1 and reaction 2 using the mean (14) of the data obtained. Reaction 1: H = 50 x 4.18 x -2.12.
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.
Polman, H., Orobio De Castro, B. & Van Aken, M. A.G. (2008). Experimental Study of the
If the temperature had been increased in batches of 5oC it would have provided a greater range of results to work with, which would create a high level of data to work with when compiling the mean and plotting the graphs as evidence.
In industry, the performance specifications for a particular pump may be known, but the tests are usually based on water as the pumping medium. For liquids of significantly higher viscosity than water, these performance curves may only be accurate at certain flow rates, or they might not be valid at all, and it might be necessary to recalibrate the specifications for higher viscosity liquids.
...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.
Third, the liquid will enter to the expansion valve with the higher pressure and leaves with the low pressure.
... temperature of 112 0C also and a pressure 2.5 bar. Cooling water is used to condense the vapor exiting column. Remaining methane and hydrogen are separated in reflux drum where the vapor stream is combined with other gases streams. The overhead of first and second separator are combined to form fuel gas. The liquid stream exiting in the bottoms of the reflux drum is pumped at pressure of 3.3 bar for discharging pressure. The pump stream is separated in two streams. One stream is to feed to tray one of the column and the other one stream is cooled down to 38 0C in heat exchanger. Then, the cooled product stream is sent to storage.
Process cd : This liquid refrigerant is collected in the liquid storage tank and later on it is expanded to low pressure and temperature by passing it through the throttle valve. At point d we have low temperature liquid refrigerant with small amounts of vapour .