How Can We Improve Precision in Volumetric Dispensing Systems for Small Volumes?

[revive]

Hello,
I've been tasked with finding a solution to a volumetric dosing system.. it's fairly straight forward in principal, however I believe the best way to address it is to ask some engineering gurus who are savvy with hydodynamics, etc.. So, without further rhetoric, here is the requirements of the project (BTW this is for our family business, hopefully something that will help save a lot of time, etc.)

Summary:
We need a way to accurately dispense 15-75 mL or water, while maintaining a consistent water temperature (also needs to be adjustable, between the ranges of 190F-210F) all while maintaining a constant 9bar of pressure during dispensing the water. Currently we are using a rotary pump set to 9bars and a boiler to maintain the water temp.. the current system lacks minute control over temperature (Although we were planning on implementing a PID to control the boiler) and completely lacks any precise control over volume (this is currently handle byt he users eye, and the process is stopped once the approx. water has been dispensed).

My thought was to implement a boiler with PID to accurately control the water temperature that is 'connected' thermally to a large 'pump block' (for lack of a better word).. the pump block would 1) maintain it's temp by thermally coupling with the boiler so temp is not reduced during dispensing and 2) would be piston based - allowing for exact control over the volume dispensed based on the travel of the piston. To move the piston I was considering a reduction-geared electric motor moving a worm drive (on one end of which would be the piston).

Project Parameters:
Accurately control the volume of water dispensed between 15 and 75mL (set by operator)
Accurately maintain water temperature between 190-210F (set by operator)
Maintain a constent 9bars of pressure while dispensing, and allowing for a 'release valve' for the pressurized line, once the water has been dispensed.

I know there are many ways to do this.. and this is just the concept that I came about. I am really hope to either find a more novel, simplified approach or to find ways to improve this current idea. Hopefully, the end result will be able to be built out of existing commercial/industrial components, that wouldn't bankrupt a small nation!

Thanks again!

 

[edgepflow]

One way to do this that I have seen work (for industrial processes at least) would be to use a heat exchanger (boiler steam on shell side and your water on tube for example). Then you could use a temperature control valve (TCV) to modulate steam flow to control your water temperature.

 

[revive]

Thank you for that recommendation! As I think about process steam, etc.. and the pressures, temp, etc. it takes to produce consistent steam to then heat the dispenser water.. I'm hoping there is a 'safer' way to accomplish it. Granted, I have very limited experience or knowledge when it comes to process steam.. but, this system has to be somewhat small in foot print (approx. 12"W x 12-24"H x12-24"D), be powered of standard 120v residential line and not pose any safety risks in the event of failure.

I could see how this would be an excellent way to produce this type of heat in an industrial setting or one using waste heat/steam in that setting.. that would be great! Unfortunately, I've got to sort out a way to accomplish these goals with what we have. :)