Chemist in an engineering world- Heat Capacity of 600mL capacity Pressure Vessel

[kdhodges2]

Hi all. I am a chemist currently working in an engineer's world. I have been tasked with obtaining the heat capacity of a 600mL pressure vessel that we will be using to conduct an array of experiments on. I have started with a known mass of water. The controller to the reactor is connected to a pc to record data (power output in Watts of the heater, temperature of the vessel contents, and the time at any point that each data point is created). How do I use this data to get the heat capacity of the reactor? Any help would be greatly appreciated.

 

[racookpe1978]

Isn't that the "heat capacity" of the 600 ml of water you are trying to heat?

How are you allowing the water to expand?
How are you controlling pressure of the water, or will it be allowed to evaporate out of the container?
What pressure of the unit?
How are you heating the container?
What is the shape and weight of the container?

Where did you get your chemistry degree? 8<)

 

[chicopee]

Aren't these reactors water cooled, also?
This is a fundamental problem all chemists would have been exposed in their chemistry and thermo. classes.

 

[kdhodges2]

In all honesty this is not a fundamental problem that all chemists would have been exposed to in thermo, because most chemists that i know do not take thermo (not even the physical chemists). If I would have ever had such classes, then I would have referred to my text book. Molecular orbital theory, phase catalysts, instrumental analysis, low-cost synthesis, reaction kinetics, electro chemistry, physical chemistry...these are the kinds of things that a chemist studies. Perhaps, I asked the question incorrectly. Maybe, I am looking for the heat coefficient of the vessel for a process (the process for obvious reasons I cannot divulge). However, the chemistry portion of my project, I have no problem with (the reaction, the kinetics of the reaction, analyzing the unwanted side reactions, and proposing a path to minimize the unwanted reactions, while maximizing the desired end-product). However, I have been tasked with assisting in the support of design of a new system (using the data I will have generated). I will reference some texts that I have available here, and, it seems that I have very well posted in the wrong area. If so, I apologize. Thanks anyway, guys (and girls).

 

[TomDOT]

I consider the question to be engineering, not chemistry. A chemist should have a general idea (and you did collect relevant data) but I would not expect most chemists to have the calculations at hand, or have all the parameters an engineer would.

 

[racookpe1978]

But back to the problem at hand.

"We" (engineering, heat transfer, ME, or chemistry or chemical engineering!) cannot answer the question as written.

"Heat capacity" of a little bit of water? 600 ml of water - assumed at room temperature, then what?

What is the start temperature, what is the end temperature - is that end temperature now (uncooled ?) or (after cooling and after the reaction?) with how much water flow? For how big a flask - which may (or may not) have significant heat capacity itself in the metal, supports, and heat transfer (?) cooling pipes? What is the reason the flask needs to be cooled?

600 ml water is very, very small. And, the smaller the system, the bigger the "little" effects of its environment matter. Melting 50 tons of steel, I don't worry about the mass of the crane hook lifting the total mass. Heating 1/2 quart of water in a timed situation on a stove top from 25 deg C to 33 degrees C, I need to calculate the heat lost from the handle of the pot and figure the room temperature changes. maybe. Or maybe not.

I assume a reaction of some kind would be going on inside? What is the reaction and how much heat is being created? What is the allowable max temperature of the system? What margin is acceptable?

We know little more than " I have a car seat and want to go faster. How big an engine do I buy?" How can we help if we don't know your problem?

 

[cloa]

I took Materials Chemistry and one unit was Thermodynamics (didn't remember much it). Thermodynamics is fundamental to chemistry. Applied Thermodynamics was in the engineering degree.

 

[GenB]

When you say ..heat capacity of the reactor.. I feel you are using electric heat when you say ..the heater.. then. The output will be related to the heater capacity say in kWh times the time powered then analyze the amount of liquid heated to come out with..power.. output. I'm not a chemist neither an eng. I'm a pv and boiler guy... I feel that some of the answers were not nice.