diff --git a/dumux/material/fluidmatrixinteractions/1p/thermalconductivityaverage.hh b/dumux/material/fluidmatrixinteractions/1p/thermalconductivityaverage.hh
index ede182b1c129b4aeceb8d2fbce523ae5413196df..720e48596098de7deecf2218b3204580e600b0a6 100644
--- a/dumux/material/fluidmatrixinteractions/1p/thermalconductivityaverage.hh
+++ b/dumux/material/fluidmatrixinteractions/1p/thermalconductivityaverage.hh
@@ -11,25 +11,41 @@
 
 namespace Dumux {
 
+/*!
+ * \addtogroup EffectiveHeatConductivity
+ * \copydetails Dumux::ThermalConductivityAverage
+ */
+
 /*!
  * \ingroup EffectiveHeatConductivity
- * \brief Relation for a simple effective thermal conductivity
+ * \brief Effective thermal conductivity based on weighted arithmetic average
  *
- * ### Average
+ * ### Average (multiple fluid phases, one solid phase)
  *
- * The effective thermal conductivity is calculated as a weighted average of the thermal
- * conductivities of the solid and the fluid phases. Additionally, the saturation is taken
- * into account.
+ * The effective thermal conductivity of `ThermalConductivityAverage`
+ * is calculated as a weighted arithmetic average of the thermal
+ * conductivities of the solid and the fluid phases. The weights are determined by the volume
+ * fraction the phase occupies. Denoting the volume fractions by \f$ n_\alpha \f$, we have
+ * \f[
+ * \lambda_\text{eff} = \sum_\alpha \lambda_\alpha n_\alpha / \sum_\alpha n_\alpha,
+ * \f]
+ * summing over both fluid and solid phases. With the porosity \f$ \phi \f$ as
+ * the sum of all fluid volume fractions, we can equivalently write
+ * \f[
+ * \lambda_\text{eff} = \lambda_\text{s} (1-\phi) + \lambda_\text{f} \phi,
+ * \f]
+ * where \f$ \lambda_\text{s} \f$ is the thermal conductivity of the solid phase,
+ * and the effective thermal conductivity of the liquid phases is computed as
+ * an arithmetic average weighted with the fluid saturations.
  */
 template<class Scalar>
 class ThermalConductivityAverage
 {
 public:
     /*!
-     * \brief Relation for a simple effective thermal conductivity \f$\mathrm{[W/(m K)]}\f$
-     *
+     * \brief Effective thermal conductivity in \f$\mathrm{W/(m K)}\f$
      * \param volVars volume variables
-     * \return Effective thermal conductivity \f$\mathrm{[W/(m K)]}\f$
+     * \return Effective thermal conductivity in \f$\mathrm{W/(m K)}\f$
      */
     template<class VolumeVariables>
     static Scalar effectiveThermalConductivity(const VolumeVariables& volVars)
diff --git a/dumux/material/fluidmatrixinteractions/2p/thermalconductivity/johansen.hh b/dumux/material/fluidmatrixinteractions/2p/thermalconductivity/johansen.hh
index 537fc27c8c03bc2737e862e73247182177673062..cd71851a7267bfa26282aa16b75b9e6e57abacf9 100644
--- a/dumux/material/fluidmatrixinteractions/2p/thermalconductivity/johansen.hh
+++ b/dumux/material/fluidmatrixinteractions/2p/thermalconductivity/johansen.hh
@@ -14,58 +14,40 @@ namespace Dumux {
 
 /*!
  * \addtogroup EffectiveHeatConductivity
- * \copydoc Dumux::ThermalConductivityJohansen
-*/
+ * \copydetails Dumux::ThermalConductivityJohansen
+ */
 
 /*!
  * \ingroup EffectiveHeatConductivity
  * \brief Relation for the saturation-dependent effective thermal conductivity
  *
- * ### Johansen Method
+ * ### Johansen (two fluid phases)
  *
- * The Johansen method (Johansen 1975 \cite johansen1977 ) computes the thermal conductivity of dry and the
- * wet soil material and uses a root function of the wetting saturation to compute the
- * effective thermal conductivity for a two-phase fluidsystem. The individual thermal
- * conductivities are calculated as geometric mean of the thermal conductivity of the porous
- * material and of the respective fluid phase.
- * The material law is:
- * \f[
- * \mathrm{[
- * \lambda_\text{eff} = \lambda_{\text{dry}} + \sqrt{(S_w)} \left(\lambda_\text{wet} - \lambda_\text{dry}\right)
- * }\f]
+ * `ThermalConductivityJohansen` \cite johansen1977 computes the thermal conductivity of dry and the
+ * wet soil material and interpolates using the Kersten number. The effective wet conductivity
+ * is based on a geometric average and the effective dry conductivity is based on a semi-emprical
+ * relation and fitted to medium quartz sand.
  *
- * with
+ * The effective thermal conductivity is given by
  * \f[
- * \mathrm{
- * \lambda_\text{wet} = \lambda_{solid}^{\left(1-\phi\right)}*\lambda_w^\phi
- * }\f]
- * and the semi-empirical relation
- *
- * \f[
- * \mathrm{
- * \lambda_\text{dry} = \frac{0.135*\rho_s*\phi + 64.7}{\rho_s - 0.947 \rho_s*\phi}.
- * }\f]
- *
- * Source: Phdthesis (Johansen1975) Johansen, O. Thermal conductivity of soils Norw. Univ. of Sci. Technol., Trondheim, Norway, 1975 \cite johansen1977
+ * \lambda_\text{eff} = \lambda_{\text{dry}} + \text{Ke} \left(\lambda_\text{wet} - \lambda_\text{dry}\right), \quad
+ * \lambda_\text{wet} = \lambda_\text{s}^{\left(1-\phi\right)} \lambda_\text{w}^\phi, \quad
+ * \lambda_\text{dry} = \frac{0.135 \rho_\text{s} \phi + 64.7}{\rho_\text{s} - 0.947 \rho_\text{s} \phi},
+ * \f]
+ * where \f$ \phi \f$ is the porosity, \f$ \lambda_\alpha \f$ is the thermal conductivity
+ * of phase \f$ \alpha \f$, \f$ \rho_\text{s} \f$ denotes the density of the solid phase, and the
+ * Kersten number is given by \f$ \text{Ke} = (\kappa S_\text{w})/(1 + (1-\kappa) S_\text{w}) \f$,
+ * with the wetting phase saturation \f$ S_w \f$ and a fitting parameter \f$ \kappa = 15.6 \f$
+ * for medium quartz sand.
  */
 template<class Scalar>
 class ThermalConductivityJohansen
 {
 public:
     /*!
-     * \brief Returns the effective thermal conductivity \f$\mathrm{[W/(m K)]}\f$ after Johansen (1975) \cite johansen1977 .
-     *
+     * \brief Effective thermal conductivity in \f$\mathrm{W/(m K)}\f$ for two phases
      * \param volVars volume variables
-     * \return Effective thermal conductivity \f$\mathrm{[W/(m K)]}\f$ after Johansen (1975) \cite johansen1977 <BR>
-     *
-     * This formulation is semi-empirical and fitted to quartz sand.
-     * This gives an interpolation of the effective thermal conductivities of a porous medium
-     * filled with the nonwetting phase and a porous medium filled with the wetting phase.
-     * These two effective conductivities are computed as geometric mean of the solid and the
-     * fluid conductivities and interpolated with the Kersten number.<br>
-     * Johansen, O. 1975. Thermal conductivity of soils. Ph.D. diss. Norwegian Univ.
-     *                    of Sci. and Technol., Trondheim. (Draft Transl. 637. 1977. U.S. Army
-     *                    Corps of Eng., Cold Regions Res. and Eng. Lab., Hanover, NH.) \cite johansen1977
+     * \return Effective thermal conductivity in \f$\mathrm{W/(m K)}\f$ for two phases
      */
     template<class VolumeVariables>
     static Scalar effectiveThermalConductivity(const VolumeVariables& volVars)
@@ -86,16 +68,16 @@ public:
 
 private:
     /*!
-     * \brief Returns the effective thermal conductivity \f$\mathrm{[W/(m K)]}\f$ after Johansen (1975) \cite johansen1977 .
+     * \brief Effective thermal conductivity in \f$\mathrm{W/(m K)}\f$ for two phases
      *
      * \param Sw The saturation of the wetting phase
-     * \param lambdaW The thermal conductivity of the wetting phase in \f$\mathrm{[W/(m K)]}\f$
-     * \param lambdaN The thermal conductivity of the nonwetting phase in \f$\mathrm{[W/(m K)]}\f$
-     * \param lambdaSolid The thermal conductivity of the solid phase in \f$\mathrm{[W/(m K)]}\f$
+     * \param lambdaW The thermal conductivity of the wetting phase in \f$\mathrm{W/(m K)}\f$
+     * \param lambdaN The thermal conductivity of the nonwetting phase in \f$\mathrm{W/(m K)}\f$
+     * \param lambdaSolid The thermal conductivity of the solid phase in \f$\mathrm{W/(m K)}\f$
      * \param porosity The porosity
-     * \param rhoSolid The density of solid phase in \f$\mathrm{[kg/m^3]}\f$
+     * \param rhoSolid The density of solid phase in \f$\mathrm{kg/m^3}\f$
      *
-     * \return Effective thermal conductivity \f$\mathrm{[W/(m K)]}\f$ after Johansen (1975) \cite johansen1977
+     * \return Effective thermal conductivity in \f$\mathrm{W/(m K)}\f$ for two phases
      */
     static Scalar effectiveThermalConductivity_(const Scalar Sw,
                                                 const Scalar lambdaW,
@@ -111,6 +93,7 @@ private:
         const Scalar rhoBulk = rhoSolid*porosity;
 
         using std::pow;
+
         const Scalar lambdaSaturated = lambdaSolid * pow(lambdaW / lambdaSolid, porosity);
         const Scalar lambdaDry = (0.135*rhoBulk + 64.7)/(rhoSolid - 0.947*rhoBulk);
         const Scalar Ke = (kappa*satW)/(1+(kappa-1)*satW);// Kersten number, equation 13
@@ -118,5 +101,7 @@ private:
         return lambdaDry + Ke * (lambdaSaturated - lambdaDry); // equation 14
     }
 };
+
 } // end namespace Dumux
+
 #endif
diff --git a/dumux/material/fluidmatrixinteractions/2p/thermalconductivity/simplefluidlumping.hh b/dumux/material/fluidmatrixinteractions/2p/thermalconductivity/simplefluidlumping.hh
index 425c719247a84a1a6263398071c12e0a9e4efec6..c00227dafd91b064d3e983f8daf4a0b724b4beac 100644
--- a/dumux/material/fluidmatrixinteractions/2p/thermalconductivity/simplefluidlumping.hh
+++ b/dumux/material/fluidmatrixinteractions/2p/thermalconductivity/simplefluidlumping.hh
@@ -9,31 +9,23 @@
 
 #include <assert.h>
 #include <algorithm>
+#warning "This header is deprecated and will be removed after 3.9. Use ThermalConductivityAverage"
 
 namespace Dumux {
 
-/*!
- * \addtogroup EffectiveHeatConductivity
- * \copydoc Dumux::ThermalConductivitySimpleFluidLumping
-*/
-
 /*!
  * \ingroup EffectiveHeatConductivity
  * \brief Relation for the saturation-dependent effective thermal conductivity
- *
- * ### Simple Fluid Lumping
- *
- * TODO: DOCUMENTATION of the fluid lumping method
+ * \deprecated This does the same as `ThermalConductivityAverage` but only works for two fluid phases
  */
 template<class Scalar>
-class ThermalConductivitySimpleFluidLumping
+class [[deprecated("Use ThermalConductivityAverage. Will be removed after 3.9.")]] ThermalConductivitySimpleFluidLumping
 {
 public:
     /*!
-     * \brief Effective thermal conductivity \f$\mathrm{[W/(m K)]}\f$
-     *
+     * \brief Effective thermal conductivity in \f$\mathrm{W/(m K)}\f$ for two phases
      * \param volVars volume variables
-     * \return effective thermal conductivity \f$\mathrm{[W/(m K)]}\f$
+     * \return Effective thermal conductivity in \f$\mathrm{W/(m K)}\f$ for two phases
      */
     template<class VolumeVariables>
     static Scalar effectiveThermalConductivity(const VolumeVariables& volVars)
@@ -50,15 +42,15 @@ public:
 
 private:
     /*!
-     * \brief Returns the effective thermal conductivity \f$\mathrm{[W/(m K)]}\f$.
+     * \brief Effective thermal conductivity in \f$\mathrm{W/(m K)}\f$ for two phases
      *
      * \param sw The saturation of the wetting phase
-     * \param lambdaW The thermal conductivity of the wetting phase in \f$\mathrm{[W/(m K)]}\f$
-     * \param lambdaN The thermal conductivity of the nonwetting phase in \f$\mathrm{[W/(m K)]}\f$
-     * \param lambdaSolid The thermal conductivity of the solid phase in \f$\mathrm{[W/(m K)]}\f$
+     * \param lambdaW The thermal conductivity of the wetting phase in \f$\mathrm{W/(m K)}\f$
+     * \param lambdaN The thermal conductivity of the nonwetting phase in \f$\mathrm{W/(m K)}\f$
+     * \param lambdaSolid The thermal conductivity of the solid phase in \f$\mathrm{W/(m K)}\f$
      * \param porosity The porosity
      *
-     * \return Effective thermal conductivity of the fluid phases
+     * \return Effective thermal conductivity in \f$\mathrm{W/(m K)}\f$ for two phases
      */
     static Scalar effectiveThermalConductivity_(const Scalar sw,
                                                 const Scalar lambdaW,
@@ -72,5 +64,7 @@ private:
         return porosity * ( (1. - satW) * lambdaN + satW * lambdaW ) + (1.0 - porosity) * lambdaSolid ; ; // arithmetic
     }
 };
+
 } // end namespace Dumux
+
 #endif
diff --git a/dumux/material/fluidmatrixinteractions/2p/thermalconductivity/somerton.hh b/dumux/material/fluidmatrixinteractions/2p/thermalconductivity/somerton.hh
index 7e21a2201677b024dac9a48be17ce3a540e2a657..d21195a72eb1c0557b578003b5a17250a6ccf6e7 100644
--- a/dumux/material/fluidmatrixinteractions/2p/thermalconductivity/somerton.hh
+++ b/dumux/material/fluidmatrixinteractions/2p/thermalconductivity/somerton.hh
@@ -4,8 +4,8 @@
 // SPDX-FileCopyrightInfo: Copyright © DuMux Project contributors, see AUTHORS.md in root folder
 // SPDX-License-Identifier: GPL-3.0-or-later
 //
-#ifndef DUMUX_MATERIAL_FLUIDMATRIX_THERMALCONDUCTIVITY_SOMERTON_HH
-#define DUMUX_MATERIAL_FLUIDMATRIX_THERMALCONDUCTIVITY_SOMERTON_HH
+#ifndef DUMUX_MATERIAL_FLUIDMATRIX_THERMALCONDUCTIVITY_SOMERTON_TWO_P_HH
+#define DUMUX_MATERIAL_FLUIDMATRIX_THERMALCONDUCTIVITY_SOMERTON_TWO_P_HH
 
 #include <algorithm>
 #include <cmath>
@@ -14,65 +14,49 @@ namespace Dumux {
 
 /*!
  * \addtogroup EffectiveHeatConductivity
- * \copydoc Dumux::ThermalConductivitySomerton
-*/
+ * \copydetails Dumux::ThermalConductivitySomertonTwoP
+ */
 
 /*!
- * \addtogroup EffectiveHeatConductivity
  * \ingroup EffectiveHeatConductivity
- * \brief Relation for the saturation-dependent effective thermal conductivity
+ * \brief Effective thermal conductivity after Somerton
  *
- * ### Somerton Method (2p)
+ * ### Somerton (two fluid phases)
  *
- * The Somerton method computes the thermal conductivity of dry and the wet soil material
- * and uses a root function of the wetting saturation to compute the
+ * The Somerton method \cite somerton1974 computes the thermal conductivity of dry and the wet soil material.
+ * It uses a root function of the water saturation to compute the
  * effective thermal conductivity for a two-phase fluidsystem. The individual thermal
  * conductivities are calculated as geometric mean of the thermal conductivity of the porous
  * material and of the respective fluid phase.
  *
- * The material law is:
+ * The effective thermal conductivity of `ThermalConductivitySomertonTwoP` is given by
  * \f[
- * \mathrm{
- * \lambda_\text{eff} = \lambda_{\text{dry}} + \sqrt{(S_w)} \left(\lambda_\text{wet} - \lambda_\text{dry}\right)
- * }
+ * \lambda_\text{eff} = \lambda_\text{g,eff} + \sqrt{S_\text{w}} \left(\lambda_\text{w,eff} - \lambda_\text{g,eff}\right)
  * \f]
  *
- * with
- * \f[
- * \mathrm{
- * \lambda_\text{wet} = \lambda_{solid}^{\left(1-\phi\right)}*\lambda_w^\phi
- * }\f]
- * and
- *
- * \f[
- * \mathrm{
- * \lambda_\text{dry} = \lambda_{solid}^{\left(1-\phi\right)}*\lambda_n^\phi.
- * }\f]
- *
+ * with \f$ S_\text{w} \f$ the water saturation,
+ * \f$ S_\text{n} \f$ the NAPL saturation, the effective phase saturations given by
+ * \f$ \lambda_{\alpha,\text{eff}} = (\lambda_\text{s})^{\left(1-\phi\right)} (\lambda_\alpha)^\phi, \alpha \in \lbrace\text{w,n,g}\rbrace \f$
+ * (geometric mean) and \f$ \lambda_\text{s} \f$ is the thermal conductivity of the solid phase.
+ * The effective conductivity \f$ \lambda_\text{g,eff} \f$ corresponds to dry conditions, whereas the
+ * effective conductivity \f$ \lambda_\text{g,eff} \f$ corresponds to wet conditions.
  */
 template<class Scalar>
-class ThermalConductivitySomerton
+class ThermalConductivitySomertonTwoP
 {
 public:
     /*!
-     * \brief effective thermal conductivity \f$\mathrm{[W/(m K)]}\f$ after Somerton (1974) \cite somerton1974 <BR>
-     *
+     * \brief Effective thermal conductivity in \f$\mathrm{W/(m K)}\f$ for two phases
      * \param volVars volume variables
-     * \return effective thermal conductivity \f$\mathrm{[W/(m K)]}\f$ after Somerton (1974) \cite somerton1974 <BR>
-     *
-     * This gives an interpolation of the effective thermal conductivities of a porous medium
-     * filled with the nonwetting phase and a porous medium filled with the wetting phase.
-     * These two effective conductivities are computed as geometric mean of the solid and the
-     * fluid conductivities and interpolated with the square root of the wetting saturation.
-     * See f.e. Ebigbo, A.: Thermal Effects of Carbon Dioxide Sequestration in the Subsurface, Diploma thesis \cite ebigbo2005 .
+     * \return Effective thermal conductivity in \f$\mathrm{W/(m K)}\f$ for two phases
      */
     template<class VolumeVariables>
     static Scalar effectiveThermalConductivity(const VolumeVariables& volVars)
     {
         using FluidSystem = typename VolumeVariables::FluidSystem;
-        static_assert(FluidSystem::numPhases == 2, "ThermalConductivitySomerton only works for two-phase fluid systems!");
+        static_assert(FluidSystem::numPhases == 2, "ThermalConductivitySomertonTwoP only works for two-phase fluid systems!");
         static_assert((FluidSystem::isGas(0) && !FluidSystem::isGas(1)) || (!FluidSystem::isGas(0) && FluidSystem::isGas(1)),
-                     "ThermalConductivitySomerton only works if one phase is gaseous and one is liquid!");
+                     "ThermalConductivitySomertonTwoP only works if one phase is gaseous and one is liquid!");
 
         constexpr int liquidPhaseIdx = FluidSystem::isGas(0) ? 1 : 0;
         constexpr int gasPhaseIdx = FluidSystem::isGas(0) ? 0 : 1;
@@ -88,23 +72,21 @@ public:
 
 private:
     /*!
-     * \brief effective thermal conductivity \f$\mathrm{[W/(m K)]}\f$ after Somerton (1974) \cite somerton1974 <BR>
+     * \brief Effective thermal conductivity in \f$\mathrm{W/(m K)}\f$ for two phases
      *
      * \param satLiquid The saturation of the liquid phase
-     * \param lambdaLiquid The thermal conductivity of the liquid phase in \f$\mathrm{[W/(m K)]}\f$
-     * \param lambdaGas The thermal conductivity of the gas phase in \f$\mathrm{[W/(m K)]}\f$
-     * \param lambdaSolid The thermal conductivity of the solid phase in \f$\mathrm{[W/(m K)]}\f$
+     * \param lambdaLiquid The thermal conductivity of the liquid phase in \f$\mathrm{W/(m K)}\f$
+     * \param lambdaGas The thermal conductivity of the gas phase in \f$\mathrm{W/(m K)}\f$
+     * \param lambdaSolid The thermal conductivity of the solid phase in \f$\mathrm{W/(m K)}\f$
      * \param porosity The porosity
-     * \param rhoSolid The density of solid phase in \f$\mathrm{[kg/m^3]}\f$
      *
-     * \return effective thermal conductivity \f$\mathrm{[W/(m K)]}\f$ after Somerton (1974) \cite somerton1974
+     * \brief Effective thermal conductivity in \f$\mathrm{W/(m K)}\f$ for two phases
      */
     static Scalar effectiveThermalConductivity_(const Scalar satLiquid,
                                                 const Scalar lambdaLiquid,
                                                 const Scalar lambdaGas,
                                                 const Scalar lambdaSolid,
-                                                const Scalar porosity,
-                                                const Scalar rhoSolid = 0.0 /*unused*/)
+                                                const Scalar porosity)
     {
         using std::max;
         using std::pow;
@@ -118,6 +100,11 @@ private:
     }
 };
 
+#ifndef DOXYGEN
+template<class Scalar>
+using ThermalConductivitySomerton [[deprecated("Use ThermalConductivitySomertonTwoP. Will be removed after 3.9.")]] = ThermalConductivitySomertonTwoP<Scalar>;
+#endif
+
 } // end namespace Dumux
 
 #endif
diff --git a/dumux/material/fluidmatrixinteractions/3p/thermalconductivitysomerton3p.hh b/dumux/material/fluidmatrixinteractions/3p/thermalconductivitysomerton3p.hh
index 33989b345afe255cc9b24fdc50956152909dfa55..5744fc49d6279042dd830aed3457626920af9317 100644
--- a/dumux/material/fluidmatrixinteractions/3p/thermalconductivitysomerton3p.hh
+++ b/dumux/material/fluidmatrixinteractions/3p/thermalconductivitysomerton3p.hh
@@ -4,8 +4,8 @@
 // SPDX-FileCopyrightInfo: Copyright © DuMux Project contributors, see AUTHORS.md in root folder
 // SPDX-License-Identifier: GPL-3.0-or-later
 //
-#ifndef DUMUX_MATERIAL_THERMALCONDUCTIVITY_SOMERTON_3P_HH
-#define DUMUX_MATERIAL_THERMALCONDUCTIVITY_SOMERTON_3P_HH
+#ifndef DUMUX_MATERIAL_FLUIDMATRIX_THERMALCONDUCTIVITY_SOMERTON_THREE_P_HH
+#define DUMUX_MATERIAL_FLUIDMATRIX_THERMALCONDUCTIVITY_SOMERTON_THREE_P_HH
 
 #include <algorithm>
 #include <cmath>
@@ -14,57 +14,41 @@ namespace Dumux {
 
 /*!
  * \addtogroup EffectiveHeatConductivity
- * \copydoc Dumux::ThermalConductivitySomerton
-*/
+ * \copydetails Dumux::ThermalConductivitySomertonThreeP
+ */
 
 /*!
  * \ingroup EffectiveHeatConductivity
- * \brief Relation for the saturation-dependent effective thermal conductivity
+ * \brief Effective thermal conductivity after Somerton
  *
- * ### Somerton Method (3p)
+ * ### Somerton (three fluid phases)
  *
- * The Somerton method computes the thermal conductivity of dry and the wet soil material.
+ * The Somerton method \cite somerton1974 computes the thermal conductivity of dry and the wet soil material.
  * It is extended here to a three phase system of water (w), NAPL (n) and gas (g).
  * It uses a root function of the water and NAPL saturation to compute the
  * effective thermal conductivity for a three-phase fluidsystem. The individual thermal
  * conductivities are calculated as geometric mean of the thermal conductivity of the porous
  * material and of the respective fluid phase.
  *
- * The material law is:
+ * The effective thermal conductivity of `ThermalConductivitySomertonThreeP` is given by
  * \f[
- * \lambda_\text{eff} = \lambda_\text{g,eff} + \sqrt{(S_w)} \left(\lambda_\text{w,eff} - \lambda_\text{g,eff}\right) +
- * \sqrt{(S_n)} \left(\lambda0_\text{n,eff} - \lambda_\text{g,eff}\right)
+ * \lambda_\text{eff} = \lambda_\text{g,eff} + \sqrt{S_\text{w}} \left(\lambda_\text{w,eff} - \lambda_\text{g,eff}\right) +
+ * \sqrt{S_\text{n}} \left(\lambda_\text{n,eff} - \lambda_\text{g,eff}\right)
  * \f]
  *
- * with
- * \f[
- * \lambda_\text{w,eff} = \lambda_{solid}^{\left(1-\phi\right)}*\lambda_w^\phi
- * \f]
- * and
- *
- * \f[
- * \lambda0_\text{n,eff} = \lambda_{solid}^{\left(1-\phi\right)}*\lambda_n^\phi.
- * \f]
- *
- * \f[
- * \lambda_\text{g,eff} = \lambda_{solid}^{\left(1-\phi\right)}*\lambda_g^\phi.
- * \f]
+ * with \f$ S_\text{w} \f$ the water saturation,
+ * \f$ S_\text{n} \f$ the NAPL saturation, the effective phase saturations given by
+ * \f$ \lambda_{\alpha,\text{eff}} = (\lambda_\text{s})^{\left(1-\phi\right)} (\lambda_\alpha)^\phi, \alpha \in \{\text{w,n,g}\}\f$
+ * (geometric mean) and \f$ \lambda_\text{s} \f$ is the thermal conductivity of the solid phase.
  */
 template<class Scalar>
-class ThermalConductivitySomerton
+class ThermalConductivitySomertonThreeP
 {
 public:
     /*!
-     * \brief effective thermal conductivity \f$\mathrm{[W/(m K)]}\f$ after Somerton (1974) extended for a three phase system
-     *
+     * \brief Effective thermal conductivity in \f$\mathrm{W/(m K)}\f$ for three phases
      * \param volVars volume variables
-     *
-     * \return effective thermal conductivity \f$\mathrm{[W/(m K)]}\f$ after Somerton (1974)
-     *
-     * This gives an interpolation of the effective thermal conductivities of a porous medium
-     * filled with the water phase (w), a NAPL phase (n) and a gas phase (g).
-     * These two effective conductivities are computed as geometric mean of the solid and the
-     * fluid conductivities and interpolated with the square root of the wetting saturation.
+     * \return Effective thermal conductivity in \f$\mathrm{W/(m K)}\f$ for three phases
      */
     template<class VolumeVariables>
     static Scalar effectiveThermalConductivity(const VolumeVariables& volVars)
@@ -83,17 +67,17 @@ public:
     }
 
     /*!
-     * \brief effective thermal conductivity \f$\mathrm{[W/(m K)]}\f$ after Somerton (1974)
+     * \brief Effective thermal conductivity in \f$\mathrm{W/(m K)}\f$ for three phases
      *
      * \param sw The saturation of the wetting phase
      * \param sn The saturation of the nonwetting phase
-     * \param lambdaW The thermal conductivity of the water phase in \f$\mathrm{[W/(m K)]}\f$
-     * \param lambdaN The thermal conductivity of the NAPL phase in \f$\mathrm{[W/(m K)]}\f$
-     * \param lambdaG The thermal conductivity of the gas phase in \f$\mathrm{[W/(m K)]}\f$
-     * \param lambdaSolid The thermal conductivity of the solid phase in \f$\mathrm{[W/(m K)]}\f$
+     * \param lambdaW The thermal conductivity of the water phase in \f$\mathrm{W/(m K)}\f$
+     * \param lambdaN The thermal conductivity of the NAPL phase in \f$\mathrm{W/(m K)}\f$
+     * \param lambdaG The thermal conductivity of the gas phase in \f$\mathrm{W/(m K)}\f$
+     * \param lambdaSolid The thermal conductivity of the solid phase in \f$\mathrm{W/(m K)}\f$
      * \param porosity The porosity
      *
-     * \return effective thermal conductivity \f$\mathrm{[W/(m K)]}\f$ after Somerton (1974)
+     * \return Effective thermal conductivity in \f$\mathrm{W/(m K)}\f$ for three phases
      */
     static Scalar effectiveThermalConductivity(const Scalar sw,
                                                const Scalar sn,
@@ -119,5 +103,14 @@ public:
 
     }
 };
+
+#ifndef DOXYGEN
+#ifndef DUMUX_MATERIAL_FLUIDMATRIX_THERMALCONDUCTIVITY_SOMERTON_TWO_P_HH
+template<class Scalar>
+using ThermalConductivitySomerton [[deprecated("Use ThermalConductivitySomertonThreeP. Will be removed after 3.9.")]] = ThermalConductivitySomertonThreeP<Scalar>;
+#endif
+#endif
+
 } // end namespace Dumux
+
 #endif