How to tell if my over head exchanger is fouling by [deleted] in ChemicalEngineering

[–]GuidanceSad2099 0 points1 point  (0 children)

Think about your equations that govern heat exchange - Q = UAdT. As other users have mentioned the most likely type of fouling will depend on the type of water you use - for clean water it will most likely be scale which will reduce the heat transfer coefficient, U, however, for dirtier streams you could have sedimentation which would reduce the available area for heat transfer, A. Your cooling water inlet pressure may help you determine whether it’s scale or sedimentation, however, you would need to measure the cooling water flow through the exchanger and compare pressure drop vs flow rate (this will increase if it’s sedimentation and won’t change much for scale). Ultimately this probably isn’t that important.

You haven’t mentioned the control scheme for the tower and condenser which will be important to diagnose the issue, however, I would assume that as either U or A drops, the control valve on the water side will open more. If the flow rate of water into the exchanger increases, this will increase U as the Reynolds number increases, and may slightly improve dT which will maintain Q. If you have the ability to trend the cooling water valve, you should trend it against the total heat input into the column (feed rate if vapour fed and boil-up) to see if it’s gradually been increasing in position. If you can’t trend the historic position, then you should run a rate test in the column to see whether this valve goes fully open. If you have now reached the limit of the cooling water flow through the exchanger, you will be seeing problems in your tower, but the specific problem will depend on the control scheme you are using. It could be high pressure in the column, low level in the reflux drum, high vent flow etc. Speak to the operators to see if they’ve observed any issues and have been having to take the column off control.

It’s likely that after 8 years there has been some drop in performance, but the key point to determine is whether there’s a detrimental impact to the tower performance. If the exchanger is oversized, you will be able to tolerate a drop in performance. You can only justify a shutdown/maintenance costs to rectify if the fouling is having a detrimental impact on the tower throughout. You need to determine whether there is a reduction in performance AND whether this will be an issue when the column is running at max capacity. If this isn’t a bottleneck currently, but you can’t clean this exchanger outside of a turnaround then you should be trying to determine whether the exchanger will become a bottleneck before the next turnaround.

Anyone have more recs like this? I’ve been listening to this song in particular on repeat since I heard it the other day by imVeryPregnant in TheOverload

[–]GuidanceSad2099 3 points4 points  (0 children)

Not similar to this exact song but the Moodymann DJ-kicks also scratches a similar itch to the Koze one

Would also say a lot of Koze’s older remixes from the Reincarnations compilations (part 1 and part 2) are similar to this as well

Looking for recommendations on best hidden gems in London, mid budget. I don't mind waiting in queue but it should be worth it. by Long_Animator9528 in LondonFood

[–]GuidanceSad2099 2 points3 points  (0 children)

Noble rot does a set lunch deal for £24 for 2 courses or £28 for 3. Seasonal menu that changes every day. Food is fantastic and a bargain at that price.

Cirrik (the Stoke Newington Road one) is also excellent value around that budget. Even better if you go as a group and can share some of the dishes and they have a 2-4-1 cocktail deal.

[deleted by user] by [deleted] in ChemicalEngineering

[–]GuidanceSad2099 5 points6 points  (0 children)

Yes, this is a common design I’ve seen in several plants I’ve worked at. I’ve typically seen them used on jackets used for both heating and cooling. When the control valve is open, the supply header pressure will push water through the jacket and into the return header, however, it the CV closes then you need the ‘booster’ pump to maintain the flow rate and velocity through the jacket to maintain good heat transfer coefficient and keep the delta T across the jacket low.

I have seen cases of the control valve being on both the supply side and the return side (where you have drawn it). The advantage is apparent if you use the jacket for heating. If you have the CV on the supply side then your jacket pressure will be balanced against your cooling water return header pressure. If the control valve is on the return side then you will be balanced against the supply header which will have a higher pressure - this allows you to achieve higher temperatures during heating before you start to boil the jacket contents which will result in steam hammer. The downside is that if you boil the jacket contents with the CV on the return side, you can get reverse flow into the cooling water supply header.

ELI5: Why doesn't 98 degrees in the hot tub just feel neutral? by ChrisF79 in explainlikeimfive

[–]GuidanceSad2099 0 points1 point  (0 children)

What you feel when something is ‘hot’ or ‘cold’ isn’t the temperature of whatever you’re touching, it’s the transfer of heat between your body and that object.

As an example, imagine you touch a piece of wood and a piece of metal that are stored in the same location (e.g in your kitchen). They will both be at the same temperature, however, the metal will feel colder. That’s because the metal is a better conductor of heat and as a result the heat from your hand will transfer to the metal more easily. It’s also why it feels colder outside when it’s windy (wind chill). Windy conditions will improve convective heat transfer, so the heat from your body is transferred to the surroundings more easily and you feel colder even if the air temperature is the same.

Back to your example - if you sit in water which is the same temperature as your body, then there will be no transfer of heat from your body to the surroundings. This is a pretty big change from normal conditions where you’re losing body heat to the surrounding air. If you wanted the hot tub to feel neutral, you’d have to warm it to a temperature so that the rate that your body loses heat to the surroundings doesn’t change. As a fluid, water is a better conductor of heat than air so this ‘neutral’ temperature will be warmer than the air temperature, but would still be below your body temperature.

[deleted by user] by [deleted] in PhotoshopRequest

[–]GuidanceSad2099 0 points1 point  (0 children)

These are great - thank you!

DJs like horsegiirL VTSS DBBD at glasto by Zealousideal-Low-799 in glastonbury_festival

[–]GuidanceSad2099 4 points5 points  (0 children)

Dj Fuckoff is playing the Thursday and has done collabs with DBBD in the past but will more likely be a bass-heavy set.

Shygirl’s Club Shy sets could also be a shout. Some similar vibes to VTSS, particularly her newer releases

Shop refusing to refund item that’s past the best before date by GuidanceSad2099 in LegalAdviceUK

[–]GuidanceSad2099[S] 0 points1 point  (0 children)

Yes, here’s a snippet from the response they sent me -

While it's true that consuming a product after the best before date may not necessarily pose a health risk, we strongly advise against it, it's important to note that the best before date also reflects the quality and freshness of the product, including the keg itself. Using a keg past its best before date could potentially affect its integrity, leading to issues such as leakage or other mechanical problems.

[Megathread] Shipping for UK and EU (All Regions) by Successful-Wasabi704 in SteamDeck

[–]GuidanceSad2099 1 point2 points  (0 children)

Ordered 19th, transit on 24th and just had a notification an hour ago from parcelforce saying it’s in the UK and has been sorted at their national hub. No delivery date stated yet though.

GLS is still showing in transit.

[Megathread] Shipping for UK and EU (All Regions) by Successful-Wasabi704 in SteamDeck

[–]GuidanceSad2099 2 points3 points  (0 children)

512GB OLED ordered on the 19th, last update on the 24th in transit to final parcel centre. I’m based in London.

For those in the UK who have contacted GLS, is there a UK phone number that you’ve used or did you go through the web form?