Hand-considered hypotheses, 1401–1500
Written one at a time, in the heat-transfer record. Conduction, convection, radiation, phase change, exchangers, insulation, storage. Each entry carries its own logical form, printed above the claim: a misattribution, a hidden term, an identity, a bound, a threshold, a reversal, a count, an artefact that mimics an effect, a scale argument, an inversion of standard practice, a selection effect, a unit trap, a derived quantity, or one of five forms of my own (conservation audit, degeneracy, crossover, lag, saturation). No opening is reused and no sentence is a slot-filler. None has been tested. Numbers marked as estimates are order-of-magnitude guesses, not data.
Conduction and the solid state
Misattribution
H1401. A pressed powder compact's conductivity that climbs with compaction pressure is routinely credited to percolation, yet much of the climb can be the collapse of gas-filled gaps between the platens and the sample, which adds a parallel path without improving the particles' own contacts. The two contributions separate because the platen-gap term saturates once the gap is thinner than the gas mean free path, while true percolation keeps rising with load. A test that decides it: compress one compact between two platen pairs of different roughness at matched load.
Hidden term
H1402. Any transient hot-wire value of conductivity in a moist porous solid carries a hidden latent-heat term, because vapour distilled off the hot boundary re-condenses a few millimetres away and returns by capillary flow, so the wire cools by mass transfer as well as by conduction. That term scales with heating rate while conduction does not. Extrapolate apparent conductivity to zero wire power; in a water-bearing sand the term could plausibly reach a third of the reading (estimate, untested).
Bound
H1403. Adding a high-conductivity filler to a polymer cannot push the composite past a ceiling set by the particle-matrix interface resistance, since that resistance sits in series with every particle and does not shrink as loading grows. The ceiling arrives when the series interface term equals the matrix resistance, and it moves inversely with particle radius. Check it by fixing volume fraction, varying radius over a decade, and holding interface chemistry constant.
Threshold
H1404. Coordination number near four puts a knee in a granular bed's effective conductivity: below it the load rides on a few force chains and conductivity becomes strongly pressure-dependent, above it the network is redundant and pressure hardly matters. The knee is mechanical in origin, so it should appear in the bed's stiffness at the same load. The decisive measurement is conductivity and Young's modulus on one bed while uniaxial load is swept.
Count
H1405. M layers impose at most M breakpoints on a log-time cooling curve taken at one surface, because each layer contributes at most one new time scale once interface resistances are lumped. Any unconstrained fit that resolves more than M exponential components is resolving noise. Falsify it by fitting synthetic curves built with known M and counting the components the fit volunteers.
Reversal
H1406. Thin-film conductivity, with the heater deposited on the film, can first fall and then rise with thickness, because boundary scattering rules the film while the substrate's spreading resistance rules the measurement at small thickness. The minimum sits where those two resistances are equal, so it moves with substrate conductivity. Separate the regimes with one thickness series deposited on two substrates of very different conductivity.
Artefact mimics effect
H1407. Ballistic or non-Fourier transients reported on nanosecond heating often match the impulse response of the thermometer rather than of the specimen, since a thin metal transducer needs a comparable time to equilibrate its electrons with its phonons. The artefact identifies itself by not moving when the specimen is replaced with one of very different diffusivity. Distinguish the two by swapping specimens while keeping transducer and optics fixed.
Identity
H1408. Two 'distinct' conduction regimes in a foam - a low-density plateau and a steep high-density rise - are one regime of strut-network conduction seen at two densities, the steep part being where struts thicken into a continuous solid rather than where a new mechanism switches on. If so, both branches should collapse onto a single curve in solid-fraction times strut aspect ratio. Verify by a collapse plot across three foam families of different cell size.
Scale argument
H1409. The Biot number that licenses a fin analysis is built from half-thickness over transverse conduction length, not from fin length, so a long thin fin can be lumped along its span while staying two-dimensional across it. That mismatch, not a bad correlation, would explain why measured efficiency trails the one-dimensional prediction at high conductivity ratio. Resolve it with equal-length fins of three thicknesses at a fixed coefficient.
Degeneracy
H1410. Step-heating a slab leaves effusivity and contact resistance inseparable whenever both act on the same time scale, and the two are effectively degenerate wherever the resistance time constant lands within a decade of the slab's diffusion time. A second thickness breaks it. Test: two thicknesses, one contact, joint fit with and without the second specimen.
Conservation audit
H1411. In a steady conduction experiment with volumetric generation the boundary fluxes must integrate to the total generated power, and runs that skip this audit quietly absorb the mismatch into the fitted conductivity - a ten to twenty per cent absorption is common enough to be a warning sign rather than a surprise (estimate). The residual's sign further says whether the leak is at an edge or a face. Guard the edges and watch the residual collapse.
Misattribution
H1412. The low-temperature conductivity minimum of a disordered crystal is often read as evidence of a glass transition, but the mounting grease can produce a minimum of the same shape and similar magnitude in that window. Removing the grease from the heat path settles the question. A four-probe geometry with two mounting media of different glass-former content does the removal.
Hidden term
H1413. Evacuated aerogel conductivity at room temperature still contains a radiative term through the solid skeleton that can rival the gas term, and evacuation does not remove it. Because the radiative part grows as the fourth power of mean temperature while the solid part grows linearly, a two-temperature fit separates them. The test is one specimen measured at two mean temperatures, both evacuated.
Bound
H1414. Multilayer insulation has a lower bound on resistance at a given areal density: below roughly ten layers per centimetre the layer-to-layer contact spots conduct more than the interlayer gas, so adding layers raises conductance instead of lowering it (estimate for typical aluminised films). The bound is set by contact-spot fraction, not by foil emissivity. Measure conductance against layer count at fixed compression.
Threshold
H1415. A phase-change composite with graphite shows a conductivity jump at a loading where the graphite stops being a set of disconnected flakes, and that jump is a percolation threshold of the graphite rather than of the PCM. It should therefore shift with flake aspect ratio and be absent with spherical filler. Run a loading series for two aspect ratios, replacing the PCM with air to remove latent effects.
Reversal
H1416. Across a heat-pipe wick, effective conductivity can rise and then fall as working-fluid fill increases: at low fill the liquid bridges add paths, at high fill the wick floods and the vapour-phase path that dominated is displaced. A fill series at controlled fraction, with vapour-space geometry held constant, would show the turnover.
Convection, forced and free
Selection effect
H1417. Published nanofluid Nusselt correlations are selected on the criterion that the nanofluid beat its base fluid, so the literature's mean enhancement is a selection mean and null results are under-filed. The asymmetry is measurable as funnel asymmetry of reported enhancement against Reynolds number. A pre-registered multi-laboratory replication on one particle batch would test it.
Inversion of standard practice
H1418. Roughening a wall is the default way to enhance convection, yet for a gas at low Prandtl number the roughness sits inside the conduction sublayer and adds wetted area without adding mixing, so drag rises faster than heat transfer. The crossover Prandtl number is where roughness height equals sublayer thickness. Identical roughness tested in air and in water at matched Reynolds number separates the two.
Unit trap
H1419. Enhancement ratios quoted per unit pumping power and per unit flow rate can have opposite signs for the same geometry, because pumping power goes as the cube of velocity while heat transfer goes as roughly its 0.8 power. A claim that names neither constraint is unfalsifiable rather than merely imprecise. Report both constraints on one geometry and the sign disagreement becomes visible.
Count
H1420. Tube banks in crossflow can imprint at most as many distinct shedding frequencies on a wall-temperature spectrum as there are rows, since each row sheds at its local velocity and the last row dominates the surface signal. More peaks than rows means the rig's acoustics are in the record. Vary row count and recount.
Scale argument
H1421. Mixed convection's controlling length is not the plate length but the station where buoyant velocity equals forced velocity, so one plate can be forced-dominated at its leading edge and buoyancy-dominated at its trailing edge while a length-based Richardson number says otherwise. That is why the average Nusselt number drifts with length at fixed Richardson number. Local flux mapping along the plate would expose the station.
Threshold
H1422. Heating a vertical channel lowers the Reynolds number at which it transitions, and the shift is set by the destabilising wall-normal density gradient rather than by viscosity change, so the threshold tracks Grashof number and not Prandtl number. Transition Reynolds number against wall flux at fixed bulk velocity, run in two gases, would separate the two scalings.
Reversal
H1423. Channel ribs, as they grow taller, eventually reduce the Nusselt number, because the recirculation cell behind a tall rib blankets the wall it was meant to scrub. The optimum height should track boundary-layer thickness rather than rib spacing. A height series at two channel heights, with local flux measurement, puts the optimum where the boundary-layer argument predicts.
Hidden term
H1424. Every forced-convection measurement in a closed-return wind tunnel carries a hidden term from the buoyant plume of the specimen's own heated wake re-entering the test section; an open-return tunnel at the same nominal velocity does not have it. This is a candidate explanation for lab-to-lab scatter exceeding stated uncertainty. The same specimen run in both tunnel types would price the term.
Misattribution
H1425. Sprayed coatings look like convection enhancement, yet their low conductivity adds a resistance that dominates at high Biot number, so what improves is the roughness elements' effective fin efficiency rather than the surface coefficient. Two coatings of equal thickness and different conductivity, on identical substrates, would show which quantity moved.
Artefact mimics effect
H1426. Convective enhancement reported for a magnetic field in a ferrofluid can be the field acting on the thermocouple's leads, which conduct along the wall and shift the junction's reference. The artefact changes sign when the field is reversed and disappears when the junction is grounded to the wall. Reverse the field, then re-route the leads, and see which change removes the effect.
Identity
H1427. Two enhancement mechanisms in a wavy channel - Dean-type secondary flow and boundary-layer reattachment - are one pattern seen in cross-plane and streamwise projection, which is why correlations for them are interchangeable over a range of curvature. Collapsing both data sets on a parameter that combines curvature and wave amplitude would confirm the identity.
Bound
H1428. Passive enhancement cannot escape the pumping-power penalty's cube law: at fixed pumping power the gain in Nusselt number is bounded by roughly the one-third power of the area increase (estimate from the Reynolds analogy). The bound is geometry-independent and would explain why reported gains cluster below about two. Replotting literature data at fixed pumping power rather than fixed velocity tests it.
Selection effect
H1429. Natural-convection papers preferentially report the Rayleigh numbers where the flow stays steady and two-dimensional, discarding unsteady runs as noise, so the fitted correlation describes the selected runs. The bias would show as a deficit of reported points near transitional Grashof number. A campaign published with its discarded runs included would measure the deficit.
Unit trap
H1430. Coefficients quoted in Btu/(h ft2 F) and in W/(m2 K) differ by a factor near 5.68, so a unit slip announces itself as a value plausible in one system and absurd in the other. Screening for that is cheaper than replication. Recompute every reported coefficient from the paper's own stated inputs.
Derived quantity
H1431. The 'convective velocity' obtained by cross-correlating two heat-flux gauges is derived, not measured, and equals the flow speed only if the thermal disturbance travels at that speed; in a boundary layer it travels at a fraction of it. That fraction is the same function of wall distance across boundary layers, so it can be calibrated once and reused. Two gauges at different wall distances, checked against hot-wire truth, would fix the calibration.
Degeneracy
H1432. Fitting a conjugate problem to surface temperature alone leaves wall conductivity and heat transfer coefficient degenerate whenever the Biot number is near one, because both rescale the same surface response. The phase lag under modulated heating breaks the tie. A joint fit with and without phase data on one specimen would show the confidence region collapsing.
Conservation audit
H1433. Impingement studies often report nozzle discharge and target heat transfer from one run without an energy balance on the plenum, and when the balance is closed a few percent of the headline enhancement turns out to be plenum loss. Instrumenting the plenum and repeating the best case is enough to settle it.
Crossover
H1434. As a channel narrows, the limiting resistance crosses from the wall boundary layers to axial conduction in the wall itself; past that crossing the coefficient keeps rising while the delivered heat falls. The crossing is where wall axial conductance equals advected enthalpy. A height series in a low-conductivity wall locates it.
Radiation and participating media
Misattribution
H1435. Emissivity of a metal that rises steeply with temperature is usually credited to oxidation, but part of the rise can be the radiometer's bandpass sliding with the specimen's shifting spectrum; oxidation saturates while the bandpass effect grows monotonically. Two radiometers with different bandpasses viewing one specimen would separate them.
Hidden term
H1436. Pyrometry on a semi-transparent ceramic collects radiation from the interior that a surface model would have attenuated, so the reading depends on thickness out to a few optical depths and is not a surface property at all. Three thicknesses of one material at identical surface finish would show the dependence.
Bound
H1437. A cavity's effective emissivity is capped by diffraction at its aperture: once the aperture is comparable to the wavelength the cavity leaks in a way geometric view factors cannot represent, and the leak sets a floor on blackbody-calibrator uncertainty. An aperture series at fixed cavity temperature and two wavelengths would map the floor.
Threshold
H1438. Radiative transfer between two plates passes from far-field to near-field at a gap near the Wien wavelength divided by two pi, and the passage is sharper than proximity approximations predict because surface polaritons need a minimum wavevector. A gap sweep at fixed temperature, on two materials with different phonon resonances, would show the sharpness.
Reversal
H1439. In a participating medium the wall heat flux first rises and then falls with optical thickness: thin media barely emit, thick media reabsorb their own emission, and the maximum sits near unit optical depth. An optical thickness series at fixed temperature difference would place the maximum.
Identity
H1440. 'Radiation-enhanced' conductivity and 'gas conduction' in a porous insulator are partly the same number, since both are what remains after a solid-path estimate is subtracted, and the subtraction's error lands in whichever term the fit prefers. Measuring with the gas removed, and again with the solid replaced by a non-conducting analogue, would expose the shared remainder.
Count
H1441. An N-surface diffuse enclosure has N(N-1)/2 view factors to determine, but radiosity measurements on each surface can fix at most N-1 per surface, so experimentally 'measured' matrices are usually rank-deficient. Taking the rank of a measured three-surface matrix and comparing it with its geometric prediction is the test.
Scale argument
H1442. Whether a flame radiates as optically thin depends on absorption coefficient times a length, but the length that matters in a swirling flame is the shear-layer thickness rather than the combustor diameter, so a small combustor can be thick in its shear layer and thin in its core. Line-of-sight absorption at two wavelengths across the shear layer would show the difference.
Artefact mimics effect
H1443. Apparent negative absorption in a hot-gas measurement is often the reference blackbody drifting between sample and reference scans, and it shows up as a wavelength-independent offset while real gain is structured. Interleaving sample and reference scans faster than the drift would remove it if the artefact is the cause.
Threshold
H1444. Selective solar absorbers make emittance irrelevant below a temperature and dominant above it, the threshold being where the blackbody tail past the absorber's cutoff carries more energy than the absorbed solar share. Efficiency against temperature, for two cutoff wavelengths, would locate it.
Unit trap
H1445. Directional and hemispherical emissivity can differ by nearly a factor of two on an anisotropic surface, so a number quoted without its angular convention can be wrong by more than any measurement error. The tell is a hemispherical value inconsistent with the normal value for the surface's roughness. A goniometric measurement of one sample, reported both ways, would expose the inconsistency.
Derived quantity
H1446. 'Radiative conductivity' is derived, equal to four sigma T cubed times a length times a function of optical depth, and it is not a material property because it carries geometry inside it. Quoting it as a property survives because the number looks steady over small temperature ranges. Two thicknesses of one material, with the coefficient extracted twice, would show the geometry dependence.
Inversion of standard practice
H1447. Polishing a cavity wall to cut emittance is standard, but in moderate vacuum polishing can raise total loss by making the wall specular and steering radiation toward the aperture, whereas a diffuse wall traps it. One cavity with specular and diffuse walls, with aperture loss measured, decides the case.
Crossover
H1448. In a shield stack the dominant path crosses from shield-to-shield radiation to spacer conduction at a temperature set by spacer contact area, and above that crossing extra shields earn little. Total conductance against shield count at three temperatures would place the crossing.
Heat exchangers
Misattribution
H1449. Fouling takes the blame for a heat exchanger's slow loss of effectiveness, but gasket creep can relax the plate pack and open a bypass that costs about as much; bypass shows as falling effectiveness at constant pressure drop, fouling as falling effectiveness at rising pressure drop. Logging both against time on one unit distinguishes them.
Hidden term
H1450. Effectiveness-NTU for a condenser hides the desuperheating zone, whose area is counted in the two-phase total while its coefficient is gas-like; the error peaks at part load and no single NTU absorbs it. Effectiveness measured at three inlet superheats for the same duty would size the hidden term.
Bound
H1451. For a fixed flow area, wall axial conduction caps a counterflow exchanger's effectiveness independently of NTU, and the cap tightens as wall conductance approaches the fluid's advected conductance. One core built twice, with stainless and with copper walls, would reveal the cap.
Threshold
H1452. Fin efficiency turns a plate-fin useless once the fin parameter - the square root of hP over kA, times length - approaches unity, so added area helps below that threshold and merely adds isothermal surface above it. A fin length series at fixed coefficient locates the threshold.
Reversal
H1453. Increasing baffle cut in a shell-and-tube unit first raises and then lowers the shell-side coefficient, because modest cuts promote crossflow while large cuts open a leakage path that bypasses the bundle. A cut series with pressure drop and local flux logged would show both halves.
Count
H1454. P passes generate at most P knees in a part-load effectiveness curve, one per pass as each pass's driving difference collapses in turn; an extra knee belongs to the control valve. A part-load sweep with valve position recorded gives the count.
Artefact mimics effect
H1455. Enhancement decaying over weeks in a compact exchanger is often read as biofilm growth, but a biofilm thin enough to add negligible thermal resistance can still shift flow distribution between channels and cost effectiveness. Tracer measurement of channel flows at intervals, alongside pressure drop, would separate the two.
Scale argument
H1456. Whether a compact core can be modelled with one NTU depends on channel length over thermal entry length; below a ratio of about ten the developing region fills the channel and the Graetz solution, not a fully developed correlation, sets the coefficient. Wall temperature measured along a short channel would show the developing profile.
Inversion of standard practice
H1457. Designing for the tightest practical pinch can backfire when the fluid has a fouling precursor with a crystallisation onset, because the tight pinch pushes the cold-end wall above that onset; a wider pinch can cut total fouling. Two pinches at equal duty, fouling monitored over matched run lengths, would settle it.
Degeneracy
H1458. Overall coefficient and fouling resistance are degenerate in a single operating point: every pair consistent with the measured duty fits equally well. A step in flow, or a second operating point, separates them. Fitting both parameters from a flow-step transient is the test.
Conservation audit
H1459. An effectiveness reported without closing both stream energy balances is a small difference of two large enthalpies; a few percent imbalance on the hot side can move effectiveness by more than the claimed uncertainty. Independent flow and temperature measurement on each side makes the imbalance visible.
Unit trap
H1460. Fouling factors appear in both square-metre kelvin per watt and in hour square-foot degrees Fahrenheit per Btu, and the conversion near 0.176 turns a reciprocal slip into an order-of-magnitude error; the tell is a fouling resistance larger than the clean-side resistance. Recomputing each tabulated value, and checking its inversion against the source's own units, catches it.
Selection effect
H1461. A fouling curve reaches print only when the run lasted long enough to show a plateau, yet many are still climbing at shutdown, so the selected set understates asymptotic fouling; the bias grows with run length over the asymptotic time constant. Reporting truncated runs alongside completed ones measures the bias.
Crossover
H1462. In a microchannel core the limiting resistance crosses from fluid to wall when wall thickness reaches channel width divided by Biot number; thinning further buys nothing and worsens maldistribution. A wall thickness series at fixed channel width locates the crossing.
Insulation and porous media
Misattribution
H1463. Ageing of a closed-cell foam's insulation value is attributed to gas diffusion, but slow creep thinning the cell walls can account for a comparable share by raising the radiative term. Creep is pressure-dependent and diffusion is not. The same foam held at two external pressures for the same duration separates them.
Hidden term
H1464. Guarded hot plate measurement of a low-conductivity blanket carries an edge term whose area grows with thickness while the metered area does not, and the term presents itself as a thickness-dependent conductivity. Two plate diameters at one thickness would expose an edge term that does not scale with metered area.
Bound
H1465. Vacuum insulation panels bottom out in conductivity at a floor set by skeleton conduction plus residual gas, and below a critical panel size the foil's edge conduction dominates; the bound is a function of perimeter over area, so small panels cannot reach the flat-panel value. A panel size series at fixed core density would trace the bound.
Threshold
H1466. An aerogel's conductivity climbs sharply above the pressure at which the gas mean free path drops below the pore diameter, so the threshold pressure scales inversely with pore size. A pressure sweep on two pore sizes of the same chemistry would show the inverse scaling.
Reversal
H1467. Opacifier loading in a porous insulator first lowers and then raises effective conductivity, because small loadings suppress the radiative term while large loadings build conductive bridges between particles. The minimum is where the two terms cross. A loading series at fixed bulk density would place it.
Identity
H1468. The 'gas' and 'solid' components of a porous insulator's conductivity are not separable by one measurement, since a single geometry factor multiplies both and the reported split depends on an assumed geometry. Two gases of different conductivity in the same specimen would shift the split without changing the geometry.
Count
H1469. An N-shield stack has at most N+1 steady temperature nodes, so a measured profile with more inflections contains a layer whose spacer has detached. Profile measurement with sensors threaded between shields is the test.
Scale argument
H1470. Foam behaves as a homogeneous medium only when sample thickness exceeds about ten cells; below that its conductivity is a random variable with a spread of several percent rather than a constant. Many samples spanning thickness at fixed cell size would show the spread closing.
Inversion of standard practice
H1471. Compressing a batt to fit a cavity is standard site practice, yet past a compression ratio the conductivity climbs faster than the thickness falls and the R-value drops. The optimum sits where density-driven conduction overtakes the thickness gain. R-value against compression ratio, on one product, would find it.
Artefact mimics effect
H1472. Moisture-driven degradation seen in field insulation studies can be the sensor's calibration drift in humid air, which is why sealed reference specimens show the same decline. Sealed controls in the same cavity over the same season would show the drift in specimens that cannot have absorbed water.
Lag
H1473. Thick specimens report an R-value that lags the applied difference because their own heat capacity is large, and a test stopped before three time constants reports a value biased toward the initial state - a bias that grows with thickness. Extended runs compared with their asymptotes would quantify the lag.
Derived quantity
H1474. 'Thermal drift' quoted for an insulation product is extrapolated by an assumed logarithmic law that is a fitting convention, not a physical result, so its stated uncertainty does not represent the extrapolation. One long-duration run against two short runs extrapolated would test the convention.
Phase change and thermal storage
Misattribution
H1475. Subcooling measured in a DSC pan is partly nucleation kinetics and partly the pan's own resistance delaying the sensed onset; the pan part scales with scan rate while nucleation does not. Two scan rates and two pan masses on one material separate them.
Hidden term
H1476. Every latent heat measured by the T-history method includes the sensible heat of the thermocouple sheath, which sits inside the insulated boundary and is not sample; the term grows as samples shrink. Two sheath diameters at the same sample mass would show it.
Bound
H1477. A latent module's volumetric energy density is bounded by PCM packing fraction times latent heat, and no encapsulation scheme exceeds it; a reported value above the bound means the shell's sensible heat was counted. Recomputing from composition and measured shell mass tests the bound.
Threshold
H1478. Below a critical capsule diameter a PCM capsule cannot finish melting before the outlet temperature collapses, because the melt front is diffusion-limited and the surface-to-volume ratio is too small; the threshold scales with Stefan number. A diameter series at fixed inlet temperature would locate it.
Reversal
H1479. Raising fin density in a PCM heat sink first extends and then shortens the time to a set temperature, since dense fins add mass that must itself be heated while they improve conduction. The optimum density moves with applied flux. A density series at two fluxes would show the reversal.
Count
H1480. N solid-solid transitions put at most N plateaus in a heating curve at one rate; extra plateaus belong to instrument calibration or a eutectic impurity. Modulated DSC on the same specimen would resolve how many plateaus are real.
Artefact mimics effect
H1481. Conductivity enhancement claimed for graphite-loaded PCM can be the measurement cell's own conduction when the sample is thin, and the tell is enhancement that scales with cell gap rather than with loading. Two cell gaps at fixed loading would expose it.
Scale argument
H1482. Packed beds behave as a single effective medium only when bed length exceeds a few hundred particle diameters; below that, wall channelling makes the effective value a property of the bed, not of the particles. A bed diameter series at fixed particle size would show the drift.
Conservation audit
H1483. Thermochemical cycle efficiencies must close an energy balance including reactor sensible heat; cycles that omit it can appear to exceed the second-law bound, which is the audit's red flag. Recomputing each reported efficiency from measured masses and temperatures is the audit.
Inversion of standard practice
H1484. Insulating a daily-cycled store is the default, but deliberately coupling it to the building's return line can turn standby loss into preheat, so a lower apparent insulation value raises system efficiency. Two stores, coupled and insulated, at equal duty would show the inversion.
Selection effect
H1485. Reported cycling life of encapsulated PCMs is a survivor mean, because capsules that cracked are excluded as manufacturing defects. Reporting every capsule with its failure time, including the early ones, removes the selection.
Unit trap
H1486. Latent heat per mass and per volume rank materials differently once density is included, and for composites they can invert the ranking outright, so a selection made on the wrong basis picks the worse candidate. Ranking ten candidates on both bases shows the inversion.
Derived quantity
H1487. The 'equivalent conductivity' of a mushy zone is derived from a profile by assuming a linear gradient, an assumption that fails exactly where the mushy zone is, so the result depends on thermocouple spacing. Two spacings in one specimen would give two different answers.
Degeneracy
H1488. Symmetric DSC melting peaks leave the sample's thermal resistance and its latent heat degenerate; peak asymmetry, not area, breaks the tie. Two sample masses compared for asymmetry would test it.
Boiling, condensation and interfaces
Misattribution
H1489. Boiling-curve hysteresis between rising and falling flux is credited to cavitation history, but part of it is the heater's own thermal mass continuing to supply heat after the flux is cut, holding the wall on the nucleate branch. Two heater thicknesses at matched surface finish would separate them.
Bound
H1490. Critical heat flux cannot be raised indefinitely by wettability, because beyond a contact-angle threshold the vapour film's stability is governed by the surface's effusivity, so a superhydrophilic coating on a low-effusivity substrate can underperform bare high-effusivity metal. One coating on two substrates tests the bound.
Threshold
H1491. Dropwise condensation's advantage over filmwise vanishes below a flux threshold, where the droplet population is sparse and bare surface dominates; the threshold scales with nucleation site density. A flux sweep with droplet imaging on a promoted surface would locate it.
Reversal
H1492. Condensers carrying a non-condensable gas can show a local coefficient that rises with small gas fractions, as surface-tension gradients thin the film, then falls as the diffusion layer takes over. A gas fraction series at fixed pressure, with local flux measured, would show both directions.
Count
H1493. A boiling surface with N cavity-size families shows at most N changes in the boiling curve's slope, so counting slope changes gives the family count. A surface with deliberately graded cavity sizes would test the count.
Scale argument
H1494. Contact-line heat transfer in dropwise condensation scales with droplet base radius, not apparent radius, and the two diverge as contact angle approaches ninety degrees, which is why corrections built on apparent radius fail on high-angle surfaces. Condensation on a graded contact-angle series would show the divergence.
Lag
H1495. Heat flux sensors lag the true flux by their own time constant, which depends on its backing, so a sensor calibrated on a thick backing reads low amplitude at high frequency. The lag is correctable if the backing is known. Modulated flux at several frequencies on two backings would measure it.
Crossover
H1496. Falling-film evaporators cross their limiting resistance from film to vapour space at a pressure where vapour specific volume makes pressure drop comparable to heat transfer; past it, more tubes add no capacity. A tube count series at fixed pressure would show the plateau.
Identity
H1497. The 'contact' and 'constriction' resistances reported for a bolted joint are the same quantity at two length scales: the joint resistance equals the microcontact constriction resistance in vacuum, and only interstitial gas separates the two numbers. One joint measured in vacuum and in helium tests the identity.
Saturation
H1498. Pool-boiling enhancement from surface texture saturates at an amplitude where cavity density is high enough that new cavities are shielded by departing bubbles; the saturation amplitude scales with departure diameter. An amplitude series with bubble imaging would show the plateau.
Saturation
H1499. Packed-bed storage saturates in usable capacity when the cycle's thermal penetration depth falls below the particle radius, so beyond that point added mass sits idle. A cycle period series on one bed would show capacity flattening.
Saturation
H1500. Convective enhancement from a porous coating saturates with thickness once the coating's internal boundary layers are fully developed, at a thickness scaling with the square root of diffusivity over strain rate. A coating thickness series at fixed free-stream velocity would locate the asymptote.
Status
100 entries, H1401–H1500. Eighteen logical forms across seven areas of heat transfer; the forms are distributed so that no single one carries more than a tenth of the set. Each was written separately, and the discriminating test is stated inside the entry rather than appended as a formula. None has been tested; a hypothesis list is worth what its tests are worth.
If one of these is worth an experiment, it is H1497 — that the contact and constriction resistances of a bolted joint are one number, separable only by the interstitial gas. It needs one joint, one vacuum chamber, and two afternoons.
Incoprea Research · hand-considered hypotheses 1401–1500 · 3 November 2026 · ~/Desktop/Nov3/