Light water coolant is at a supercritical pressure at 25MP

[Milentije]

I don't get it.I found out that light water coolant is at a supercritical pressure at 25MPa.The boiling phenomenon disappears at supercritical pressure but the specific heat shows a peak around the pseudo-critical temperature.There is no phase change from liquid to gas,so the coolant flow in this reactor is single phase.
Anyone has idea?

 

[Astronuc]

What is it that one does not get. The behavior and properties of supercritical water is well known. It is used in supercritical coal plants and in the chemical process industry.

These might be of interest, particularly the last two papers -

Supercritical water has properties of both liquid and gas.

First some general Physical Properties of Water
http://www.science.uwaterloo.ca/~cchieh/cact/applychem/waterphys.html

Supercritical fluids
http://www.kobelco.co.jp/p108/p14/sfe01.htm

Characteristics and uses of supercritical water
http://www.kobelco.co.jp/p108/p14/sfe02.htm


Paper on SCLWR concept
http://www.tkk.fi/Units/AES/courses/crspages/Tfy-56.181_03/Danielyan.pdf


This paper might be of interest.
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V4D-4GPW6PH-1&_user=10&_coverDate=11%2F30%2F2005&_rdoc=6&_fmt=summary&_orig=browse&_srch=doc-info(%23toc%235756%232005%23997649977%23607278%23FLA%23display%23Volume)&_cdi=5756&_sort=d&_docanchor=&view=c&_ct=7&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=7554bc0ba095f6586e41b2ae3a1a7647

Abstract

This literature survey is for heat transfer to supercritical water flowing in channels. The objectives are to assess the work that was done and to understand the specifics of heat transfer at these conditions. Our exhaustive literature search, which included over 450 papers, showed that the majority of experimental data were obtained in vertical tubes, some data in horizontal tubes and just a few in other flow geometries including bundles. In general, the experiments showed that there are three heat transfer modes in fluids at supercritical pressures: (1) normal heat transfer, (2) deteriorated heat transfer with lower values of the heat transfer coefficient (HTC) and hence higher values of wall temperature within some part of a test section compared to those of normal heat transfer and (3) improved heat transfer with higher values of the HTC and hence lower values of wall temperature within some part of a test section compared to those of normal heat transfer. The deteriorated heat transfer usually appears at high heat fluxes and lower mass fluxes. Also, a peak in HTC near the critical and pseudo-critical points was recorded. Due to the limited number of publications that are devoted to heat transfer in bundles cooled with water at supercritical pressures, more work is definitely needed to provide the additional information for design purposes.

Supercritical Water Heat Transfer
http://www.touchbriefings.com/pdf/2402/corradini.pdf


There are certainly challenges related to materials degradation, especially if the primary system is designed for a lifetime of 60 years. Corrosion/erosion will be an issue IMO. One area that is not well known is the added effect of radiolysis on corrosion.

 

[Milentije]

Thanks Actronuc,now I realize what is going on.
By the way english is not my first language!

 

[davefitz]

more papers re: supercritical heat transfer

some papers found to be useful ,as applied to the use of supercritical heat transfer in fossil fired boilers:

BS Shiralkar + Peter Griffith "Deterioration in Heat Transfer to Fluids at Supercritical Pressure and High Heat Flux" ASME J of heat trans Feb 1969 pp 27-36

HS Swenson et al " Heat transfer to supercritical water in smooth bore tubes" ASME j of heat tran nav 1965 pp 477-483

NM Shurr et al " A numerical analysis of heat transfer to fluids near the thermodynamic critical point inlcuding the thermal entrance region" ASME j of heat trans Nov 1976 pp 609-615.

Remember: when utilizing a correlation for a multi-channel circuit , you would need to determine the flow conditions for the "worst" tube , based on a static stability or thermal hydraulic sensitivity analysis of the circuit. Average tube properiies do not govern the desing.

 

[davefitz]

I just read a few papers on the gen IV SCWR, and am very surprised that the issues uncovered in the 1950's ( when it was first proposed) aren't being addressed.

for example, the below papers by Hyman et al use relatively simple calculations of circuit thermal hydraulic "sensitivity" to illustrate that heating the fluid from 400 F to 1000 F in one mother of all passes is prone to extraordinary overheat at the outlet of the "worst" channel. It should be interesting to read the final report of whoever is calculating the gen IV sensitivity and stability characteristics.

"Flow distribution among parallel heated channels " AR Gruber, SC Hyman, Chem Eng Prog V2 no2 Jun 56 pp 199-205
"Control of flow distribution by mixing headers" SC Hyman, AR Gruber, Ljoseph Chem Eng Prog v4 no 1 Mar 58 pp33-36 }

 

[Astronuc]

I just read a few papers on the gen IV SCWR, and am very surprised that the issues uncovered in the 1950's ( when it was first proposed) aren't being addressed.

for example, the below papers by Hyman et al use relatively simple calculations of circuit thermal hydraulic "sensitivity" to illustrate that heating the fluid from 400 F to 1000 F in one mother of all passes is prone to extraordinary overheat at the outlet of the "worst" channel. It should be interesting to read the final report of whoever is calculating the gen IV sensitivity and stability characteristics.

"Flow distribution among parallel heated channels " AR Gruber, SC Hyman, Chem Eng Prog V2 no2 Jun 56 pp 199-205
"Control of flow distribution by mixing headers" SC Hyman, AR Gruber, Ljoseph Chem Eng Prog v4 no 1 Mar 58 pp33-36 }

I would say that the issues of stability and hot channel are not being addressed. AFAIK, each concept is being evaluated with sophisticated CFD codes. In addition, one lab is looking at coupling a transport theory based core physics codes with a CFD code precisely to look at hot channel and stability issues (feedback from moderator density/phase changes). Back in the 1950's, they didn't have the 50 years of experience we have gained since then.