Sir, u can design the equipment as condenser if condensate outlet temperature is 100 Deg C. This will be compact. If u want brought down condesare temperature to 18 Deg C, counter current heat exchanger can be designed, but size of the equipment will be increased. Mass flow rate generally governed by process system requirement. Designer may not have control over this parameter

As a first estimate, ignore condensate subcooling (i.e. assume water outlet temperature equal to the saturation temperature), nd calculate the condensate mass flow rate from a heat balance (m*c_p*detaT)_cold fluid=(m*h_fg)steam, where h_fg is the latent heat of condensation.

Depending on your heat exchanger geometry (shell-and-tube, plate, tube-in-tube etc) and vapor flow orientation it may be possible to reduce the steam flow rate somewhat, but most likely you will position a condensate trap at the heat exchanger exit, leading to no candensate subcooling.

Best of luck in your design task!

Nelaturi V Raghavaiah Thank you for your answer, I have no desire to bring down the condensate temperature further so i will design with an outlet of 100C as you've said.

Norbert Lümmen Thank you, I will be taking this approach!

You may want to note the quality of the steam (dryness) as it will determine the energy involved

Every thing above is correct but I would suggest you look at the convection coefficients for steam and condensate and see if it is any optimization possible since the 2 values are not equal. You will have 3 zones one with only steam, one where the steam will condense and a third (eventually) with hot water.

Your interest is also to have the most compact solution thus ...

Good luck

Before giving any response, can you advise/ provide information for the following? (The above responses cover most of your thermal design requirements.)

(i) What is the required duty?

(ii) What is the fluid to be heated? Can you confirm its temperature range and fluid properties? Is it toxic? Does its properties change significantly with temperature?

(iii) Do you have a rough size for the exchanger/condenser?

(iv) Do you have access to software such as the suites provided by HTRI and HTFS?

(v) What is the source of heat? How is this provided?

(vi) What happens to fluid to be heated if you get an upset condition resulting in too much steam being introduced?

(vii) Would any leak and cross contamination of the fluids lead to a dangerous situation?

If you are using steam at 100C and it is a condensing application, you will have a pressure of roughly atmospheric pressure and I am wondering what drives the steam flow? Condensing steam has a good heat transfer coefficient in most applications so is usually a good choice - but it is still hot and you must take suitable precautions.

In many industrial applications one measures the outlet temperature of the fluid to be heated and use this to control the inlet steam flow - but then they usually provide the steam at roughly five (5) bar g. If there is any boiling / condensation of the process fluid its temperature profile becomes flat and temperature control becomes very difficult. If you know the fluid's properties you can use velocity in the external pipework to give good control, but this does demand consistent fluid properties.

Lower pressures can be used but then all pipework, etc. becomes very large.

There is a company in the UK called Spirax-Sarco and they provide useful information for the design of steam equipment. They give a remote design course as well as providing design manuals. It use to be a very low cost course but you must verify this.

If you are doing mechanical design, please ensure that in any condensing application you design for full vacuum as if you shut in the exchanger full of steam, as it condenses due to heat loss, its pressure will drop. Under similar temperature, etc. conditions the density of steam is significantly less than the density of water.

There is a lot of legislation in the UK around the use of steam.

Don't forget that you will need safety valves and their discharge needs to be taken to a safe location.

Hope that this helps. Regards, Stephen.

With the given parameters values, I will advise you try simulation with Hysys.

Good luck.

Enthalpy curve

You have inlet temperature

Martell Brighten use aspen Hysys to simulate your process this simulation will help you.

Hello,

I agree with Lawal Alidu and Mohamed Nasser, you can also try Aspen Plus EDR ( for a more rigorous model). However, as a first approach you can try a conventional HEX in Aspen. You can check the Design Mode and then you will get the degrees of freedom necessary for your simulation (as input variables in Aspen). You can use a Design Specification (varying the steam mass flow) in order to reach the conditions and the outlet of the equipment. Once this is fixed with your conditions you can run the model.

Good luck!!

This Link Maybe Useful:

https://www.spiraxsarco.com/learn-about-steam/steam-engineering-principles-and-heat-transfer/steam-consumption-of-heat-exchangers

dear Martell Brighten

the main objective when someone want to deisgn a hear exchenger is to use the latent heat of steam. By this logic one aims to get the most heat transfer by the condensation of steam and not subcooling the steam.

the approach to these calculations would be like this

1. your process stream has fixed flow, properties, inlet temperature and you need it to be in outlet at 40 C. so the heat duty of your heat exchanger is fixed.

2 steam is saturated, and you will need to meet the heat duty. assume total condensation at first. this will change snce the geomtery will casue pressure drop and less efficient heat transfer

We can assume a constant temperature of steam and condensate. We can also assume that the temperature of the condensate decreases. This is only the energy balance under steady conditions.

Another sad "orphan" thread - abandoned after birth by its creator.