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This paper aims to study the fluid flow and heat transfer through a spiral double-pipe heat exchanger. Nowadays using spiral double-pipe heat exchangers has become popular in different industrial segments due to its complex and spiral structure, which causes an enhancement in heat transfer.

In these heat exchangers, by converting the fluid motion to the secondary motion, the heat transfer coefficient is greater than that of the straight double-pipe heat exchangers and cause increased heat transfer between fluids.

The present study, by using the Fluent software and nanofluid heat transfer simulation in a spiral double-tube heat exchanger, investigates the effects of operating parameters including fluid inlet velocity, volume fraction of nanoparticles, type of nanoparticles and fluid inlet temperature on heat transfer efficiency.

After presenting the results derived from the fluid numerical simulation and finding the optimal performance conditions using a genetic algorithm, it was found that water–Al₂O₃ and water–SiO₂ nanofluids are the best choices for the Reynolds numbers ranging from 10,551 to 17,220 and 17,220 to 31,910, respectively.

There is almost a consensus amongst Muslim scholars that the most crucial problem faced by the Muslim world is in the prevailing ideas (including sanctification, archaism, the common paradigm, the absence of the role of the intellectual, etc.) which formulate people’s thoughts and determine their options. There will not be a genuine renaissance of Islam without updating these ideas and emerging from the cocoon of the past. This can be done through a modern approach which would respond to the changes by looking towards the future rather than towards the past. This study aims to identify the intellectual aspects of this crisis and how this crisis has formed and influenced Islamic banking.

To analyse this crisis, the methodology called causal layered analysis (CLA) is used, which is drawn from the field of strategic foresight and designed by Inayatullah (2002). CLA is designed on the basis that the way to understand the nature of the problem will determine the proposed solutions, by diving through the surface phenomena of the problem to the depth of the “motors” of the crisis.

The author finds that Islamic banking is the offspring of its incubator ideas and reform, and the change and progress of Islamic banking can only deal with a critical approach of these ideas; Islamic banking promotes itself as an alternative to conventional banking, but this has not been achieved except on the level of form rather than substance; Islamic banking is a movement within a variable reality, and inertia in specific form and context will keep it in a state of crisis and may lead to its demise.

To the author’s knowledge, this is the first study showing the roots of the ideas making up the fabric of banking in the Muslim world and the repercussions of intellectual crisis on Islamic banking.

This paper aims to delve in an aspect of monetary economics, addressing its Islamic wing in general and dinar advocates in particular.

The paper argues that calls to reinstitution of dinar currencies are not only anachronistic and unnecessary but also counter-productive and potentially un-Islamic.

The paper further posits that regardless of the nature of economy, legal tender fiat money and bank money are of the same genus, and treating them otherwise is not consistent with Islamic jurisprudential precepts.

The study also highlights that mismanagement, avarice and human follies are to blame for financial maladies; regression to metallic currency is a panacea to neither the conundrums nor Islamic.

Using turbulators, obstacles, ribs, corrugations, baffles and different tube geometry, and also various arrangements of these components have a noticeable effect on the shell and tube heat exchangers (STHEs) thermal-hydraulic performance. This study aims to investigate non-Newtonian fluid flow characteristics and heat transfer features of water and carboxyl methyl cellulose (H₂O 99.5%:0.5% CMC)-based Al₂O₃ nanofluid inside the STHE equipped with corrugated tubes and baffles using two-phase mixture model.

Five different corrugated tubes and two baffle shapes are studied numerically using finite volume method based on SIMPLEC algorithm using ANSYS-Fluent software.

Based on the obtained results, it is shown that for low-mass flow rates, the disk baffle (DB) has more heat transfer coefficient than that of segmental baffle (SB) configuration, while for mass flow rate more than 1 kg/s, using the SB leads to more heat transfer coefficient than that of DB configuration. Using the DB leads to higher thermal-hydraulic performance evaluation criteria (THPEC) than that of SB configuration in heat exchanger. The THPEC values are between 1.32 and 1.45.

Using inner, outer or inner/outer corrugations (outer circular rib and inner circular rib [OCR+ICR]) tubes for all mass flow rates can increase the THPEC significantly. Based on the present study, STHE with DB and OCR+ICR tubes configuration filled with water/CMC/Al₂O₃ with f = 1.5% and d_np = 100 nm is the optimum configuration. The value of THPEC in referred case was 1.73, while for outer corrugations and inner smooth, this value is between 1.34 and 1.57, and for outer smooth and inner corrugations, this value is between 1.33 and 1.52.