8 replies to this topic

[Art Montemayor]

Kay:

One doesn’t calculate a mechanical design for a double pipe condenser. One simply applies the assembly of one pipe inside another, welding the seams between both pipes. A method is designed for supporting the assembly of more than one double pipe – if such is required.

The mechanical design should follow the following guidelines:

• The assembly should be sloped (to allow for saturated condensate removal as it is being formed);
• The entrance of the vapor should be at the top of the outer pipe, with the flow of vapor continuing inside the outer pipe towards the exit end where it is totally condensed or continues down into another double-pipe assembly that is also sloped (like the first);
• Since sloping is a requirement, this presents a problem because the two assemblies are sloped in opposite directions if both assemblies are piped in series;
• The best way to achieve a good configuration is to lay multiple, sloped assemblies (if such are needed) side-by-side, all piped to inlet and outlet headers; this is a horizontal layout of assemblies and takes up a rather large footprint. But it is a requirement due to the condensate drainage from each.

[Art Montemayor]

Kay:

My statement that there are no calculations involved in a double-pipe heat exchanger is a correct one. Calculations are involved with respect to pressure vessels; however, normal pipe ratings already exist that have calculated the ratings for the pipe - so you use those and by-pass any pipe calculations as to wall thickness at the pressure and temperatures involved.

A mechanical design for a double-pipe exchanger is a series of mechanical fabrication drawings - all based on a double-pipe exchanger's Data Sheet information. You have to develop sketches and dimensions - as well as methods of assembly for the unit. The sketches are preliminary and should be of what you conceptually visualize the unit to be like. The fabrication drawings are formal instructions to the fabrication shop to build the unit for you, so you have to be correct, accurate, practical, and specific in your fabrication instructions because they will be followed religiously by people who regard you as the expert in detailing what it is that you want fabricated.

[Art Montemayor]

Kay:

I am presently visiting my grandchildren for my vacation, and do not have my personal library or files available. I am stuck with an Apple computer and can't use the Excel engineering graphics. Therefore, I can't be of much help on the limited information you supply.

Where is your Data Sheet? The process calculations should already be finished if you intend to do a mechanical design (as you stated). Where are the mechanical sketches? Our members can't reply to general statements ("having issues with sizes for the valves"); you must employ specific questions and back that up with specific basic data. what do you mean by "height" and "width" of a double-pipe condenser? There are only two pipes involved in such a unit; that fixes the width, depth, and height. Without engineering sketches or diagrams, it is very difficult to understand your dilemma.

[srfish]

Kay,

Since Art is on vacation I will see if I can help.

The heat exchanger surface you show iis a single pipe within a pipe. There is no return bend connecting 2 pipe sections. The only height and width would be the O.D. (outer diameter) of the outside pipe.

The nozzle sizes depend on how much pressure drop is available (up to a certain point).

There is an error in the section of the spreadsheet named: "Double Pipe Condenser Specification". Ii shows The inner pipe and the outer pipe with the same dimensions.